Method and device for determining lbt mode, and method for implementing lbt mode switch

ABSTRACT

The present disclosure provides a method and an apparatus for determining a Listen Before Talk (LBT) mode, as well as a method for LBT mode switching. The method includes: determining ( 100 ) an LBT mechanism and/or an LBT mechanism parameter set based on related indication information and/or priority information and/or measurement information; and performing ( 101 ), by a transmitting device, contention-based channel access based on the determined LBT mechanism and/or LBT mechanism parameter set. With the present disclosure, an LBT mode can be determined. With the selection of the LBT mode, it is possible to avoid waste of channel resources and indication information due to an improper LBT mode, thereby improving an efficiency of contention-based channel access.

TECHNICAL FIELD

The present disclosure relates to wireless communication technology, andmore particularly, to a method and an apparatus for Listen Before Talk(LBT) mode switching.

BACKGROUND

With the rapid growth of data traffic, there are increasingly higherdata transmission loads on carriers in licensed spectrums. Hence, it isan importation trend of evolution in the future development of Long TermEvolution (LTE) to offload the data traffic on the licensed carriers tocarriers in unlicensed spectrums. The unlicensed spectrums have severaladvantages.

People do not need to buy them—their spectrum resources are free orinexpensive. They have low admission requirements so both individualsand companies can deploy them. They include frequency bands at 5GHz and2.4GHz and have a large bandwidth available. They have a characteristicof resource sharing, allowing several different systems or severaldifferent operators of one single system to operate therein, such thatthe spectrum utilization efficiency can be improved by means of resourcesharing.

In view of the above advantages of the unlicensed spectrums, the LTERelease 13 has started a research since September 2014, including animportant research topic regarding operations of the LTE system usingcarriers in the unlicensed spectrums. The techniques involved in thistopic enable the LTE system to use the currently existing carriers inthe unlicensed spectrums, so as to increase the potential spectrumresources of the LTE system significantly, allowing the LTE system tohave a further reduced cost of spectrum resources. While bringingbenefits for the development of the LTE system, the use of the carrierresources in the unlicensed spectrum causes a problem of faircoexistence between a Licensed-Assisted Access (LAA) system and othercommunication techniques (e.g., Wi-Fi). In addition, according toregulations in some areas, in order to access carriers in the unlicensedspectrum, a Listen Before Talk (LBT) mechanism is required to beperformed first. That is, an LAA device, such as an evolved NodeB and/ora User Equipment (UE), has to fulfill the LBT requirement in thoseareas, in order to coexist friendly with other communication techniques(e.g., Wi-Fi).

With further researches in the LTE-U topic in the R13 LAA SI stage,finally in the first meeting of the WI stage (3GPP RANI #82), it hasbeen agreed as to whether a UE needs to apply the LBT mechanism beforean uplink transmission. That is, it is believed that the UE must applythe LBT mechanism individually before transmission, so as to improve theuplink performance of the system. Meanwhile, there are several types ofcandidate modes available for the uplink LBT and there are differentconfigurations in on mode. Here, the candidates of uplink LBT modesinclude: LBT Category (Cat) 2, an LBT mechanism without random back-off;LBT Cat3, an LBT mechanism with random back-off and a fixed ContentionWindow (CW) size; and LBT Cat4, an LBT mechanism with random back-offand a variable CW size. Further, depending on different priority levelsor requirements, some set of parameters for some LBT mechanism may beneeded.

Hence, while some operational assumptions have been agreed currently forthe LAA uplink, there are no solutions defined for switching between thecandidates of the uplink LBT modes or between different sets ofconfiguration parameters in one LBT mode. If an improper LBT mode isselected, e.g., when only one configured LBT mode or parameter set isadopted in an uplink system, its performance will be degraded.Furthermore, if an improper LBT mode is configured, there may beproblems such as waste of resources allocated to a UE, waste of uplinkindication information, low contention-based access rate, or unfairness.

SUMMARY

In order to solve the above problems, the embodiments of the presentdisclosure provide a method and an apparatus for LBT mode switching,which clearly defines an LBT mode for contention-based channel accessand is capable of avoiding problems due to improper selection of LBTmode.

The object of the present disclosure is achieved by providing a methodfor Listen Before Talk (LBT) mode switching. The method includes:determining an LBT mechanism and/or an LBT mechanism parameter set basedon related indication information and/or priority information and/ormeasurement information.

Optionally, the method further includes: performing, by a transmittingdevice, contention-based channel access based on the determined LBTmechanism and/or LBT mechanism parameter set.

Optionally, the related indication information includes: a size of datapacket to be transmitted, a number of successive scheduled subframes,one or more bits configured in physical Downlink Control Information(DCI) signaling, a broadcast scheme, a time-domain length of a gapbetween an uplink transmission burst and a downlink transmission burst,an identity in an LBT list signaled from a base station, a position of ascheduled subframe in a transmission burst or in successive uplinksubframes, a length of one transmission burst, and/or a carrier scenariofor transmission of a scheduling instruction.

Optionally, the priority information includes: a Quality of Service(QoS) priority for a traffic type, or a priority of a channel, apriority of a signal, a priority of a logical channel, and/or thepriorities of the channel, signal and logical channel.

Optionally, the priority information further includes: a priority of aphysical transmission channel, obtained by mapping a level of thepriority of the logical channel to the physical transmission channel.

Optionally, the measurement information includes: Channel StateInformation (CSI) within a predetermined time length, a Reference SignalReceived Power (RSRP) within a predetermined time length, a ReferenceSignal Received Quality (RSRQ) within a predetermined time length,Hybrid Automatic Repeat reQuest-Acknowledge (HARQ-ACK) information, orinformation on a measured interference.

Optionally, the LBT mechanism includes an LBT mechanism without randomback-off and an LBT mechanism with random back-off.

Optionally, the LBT mechanism without random back-off includes an LBTCat2 mechanism and an enhanced LBT Cat2 mechanism.

Optionally, the LBT Cat2 mechanism is an LBT mechanism in which only oneClear Channel Assessment (CCA) is performed.

Optionally, the enhanced LBT Cat2 mechanism is an LBT mechanism in whichtwo or more Clear Channel Assessments (CCAs) are performed.

Optionally, each CCA has a fixed or random start position.

Optionally, each CCA has a time length of 34 microseconds (μs), 25 μs,20 μs, 16 μs, 9 μs or 4 μs.

Optionally, the LBT mechanism with random back-off includes an LBT Cat4mechanism having a variable Contention Window (CW) size and an LBT Cat3mechanism having a fixed CW size.

Optionally, the LBT Cat4 mechanism includes at least one of thefollowing parameters: a first Clear Channel Assessment (CCA); a deferperiod; a maximum CW, CWmax; a minimum CW, CWmin; and a random back-offvalue, N.

Optionally, the defer period includes defer time plus n multiplied byslot, or n multiplied by slot plus defer time, where n is an integer inan interval of [0, 2], slot has a time-length of 9 μs, and the defertime is 16 μs.

Optionally, the first CCA has a time length of 34 microseconds (μs), 25μs, 20 μs, 16 μs, 9 μs or 4 μs.

Optionally, the random back-off value N is indicated by a base station,generated randomly or predetermined.

Optionally, the random back-off value N is a value selected randomlyfrom an interval of [0, q-1], where q is a value selected randomly froman interval of [CWmin, CWmax].

Optionally, the LBT mechanism parameter set includes: when the LBTmechanism is an LBT Cat4 mechanism, at least one of: a minimum CW; amaximum CW; and a component n of a defer period, for the LBT Cat4mechanism; or when the LBT mechanism is an LBT Cat2 mechanism, a timelength of a Clear Channel Assessment (CCA) for the LBT Cat2 mechanism.

Optionally, when the LBT mechanism is the LBT Cat4 mechanism, themechanism parameter set further includes: a time length of a first CCA.

Optionally, the method further includes, when the LBT mechanism is theLBT Cat4 mechanism: dividing the LBT mechanism parameter set intorespective categories depending on different values of the maximum CWand the minimum CW and/or a size of the component n in the defer periodin the parameter set for the LBT Cat4. The respective categories of theLBT mechanism parameter set can have their respective CW intervals,corresponding to their respective maximum CWs and minimum CWs, partiallyoverlapping or not overlapping each other.

Optionally, the method further includes, when the LBT mechanism is theLBT Cat2 mechanism: dividing the LBT mechanism parameter set intorespective categories depending on different time lengths of CCA for theLBT Cat2.

Optionally, the method further includes, when the LBT mechanism includesthe LBT Cat2 and the LBT Cat4: dividing the LBT mechanism parameter setinto respective categories depending on different time lengths of CCA,sizes of CWs and/or components n in the defer period.

Optionally, the respective categories of the LBT mechanism parameter setare based on priorities, predefined, divided based on values ofavailable maximum CWs, divided based on time lengths of CCA, indicatedby a base station, or indicated dynamically in Downlink ControlInformation (DCI).

Optionally, when the related indication information is a size of datapacket to be transmitted, the operation of determining the LBT mechanismand/or LBT mechanism parameter set based on the related indicationinformation includes: preconfiguring a set of sizes for data to betransmitted corresponding to respective LBT mechanisms and/or LBTmechanism parameter sets; and selecting the LBT mechanism and/or LBTmechanism parameter set corresponding to the size of data packet to betransmitted.

When the switching related information is a number of successivescheduled subframes, the operation of determining the LBT mechanismand/or LBT mechanism parameter set based on the related indicationinformation includes: preconfiguring a set of for numbers of successivescheduled subframes corresponding to the respective LBT mechanismsand/or LBT mechanism parameter sets; and selecting the LBT mechanismand/or LBT mechanism parameter set corresponding to the number ofsuccessive scheduled subframes.

When the switching related information is one or more bits configured inDownlink Control Information (DCI) signaling, the operation ofdetermining the LBT mechanism and/or

LBT mechanism parameter set based on the related indication informationincludes: preconfiguring a set of bit information and/or numbers of bitsconfigured in the DCI signaling corresponding to the respective LBTmechanisms and/or LBT mechanism parameter sets; and selecting the LBTmechanism and/or LBT mechanism parameter set corresponding to the bitinformation and/or the number of bits configured in the DCI signalingfor contention-based channel access.

When the switching related information is a broadcast scheme, theoperation of determining the LBT mechanism and/or LBT mechanismparameter set based on the related indication information includes:determining the LBT mechanism and/or LBT mechanism parameter set basedon an identity in an LBT list set, a category of an LBT mechanismparameter set, an LBT mechanism and/or an LBT mechanism parameter setbroadcasted to a transmitting device.

When the switching related information is a time-domain length of a gapbetween an uplink burst and a downlink burst, the operation ofdetermining the LBT mechanism and/or LBT mechanism parameter set basedon the related indication information includes: preconfiguring a set oftime-domain lengths for the gaps corresponding to the respective LBTmechanisms and/or

LBT mechanism parameter sets; and determining the LBT mechanism and/orLBT mechanism parameter set corresponding to the time-domain length ofthe gap between the uplink burst and the downlink burst.

When the switching related information is an identity in an LBT listsignaled from a base station, the operation of determining the LBTmechanism and/or LBT mechanism parameter set based on the relatedindication information includes: preconfiguring an information list ofLBT mechanisms for switching, to be shared between that transmittingdevice and the base station; and determining, by the transmittingdevice, the LBT mechanism and/or LBT mechanism parameter set based on anidentity in the information list as indicated or broadcasted by the basestation.

When the related indication information is a position of a scheduledsubframe in a transmission burst or in successive uplink subframes, theoperation of determining the LBT mechanism and/or LBT mechanismparameter set based on the related indication information includes:preconfiguring positions of the scheduled subframe in the transmissionburst or positions of the scheduled subframe in the successive uplinksubframes corresponding to respective LBT mechanisms and/or LBTmechanism parameter sets; and determining the LBT mechanism and/or LBTmechanism parameter set based on the position of the scheduled subframein the transmission burst or in the successive uplink subframes.

When the related indication information is a carrier scenario fortransmission of a scheduling instruction, the operation of determiningthe LBT mechanism and/or LBT mechanism parameter set based on therelated indication information includes: determining the LBT mechanismand/or LBT mechanism parameter set based on same-carrier scheduling orcross-carrier scheduling.

Optionally, the method further includes, when the switching relatedinformation is a time-domain length of a gap between an uplink burst anda downlink burst: preconfiguring a set of time-domain lengths for thegaps corresponding to respective LBT mechanisms and/or LBT mechanismparameter sets; and determining to apply no LBT mechanism and/or LBTmechanism parameter set when the time-domain length of the gap betweenthe uplink burst and the downlink burst is smaller than a predeterminedthreshold.

Optionally, the operation of determining the LBT mechanism and/or LBTmechanism parameter set based on the related indication information andthe priority information includes:

determining the LBT mechanism based on the related indicationinformation, and then determining the LBT mechanism parameter setcorresponding to the LBT mechanism based on different priority levels inthe priority information.

Optionally, the operation of determining the LBT mechanism parameter setcorresponding to the LBT mechanism based on different priority levels inthe priority information includes: determining a corresponding LBTmechanism, LBT mechanism parameter set or category of LBT mechanismparameter set based on different priorities contained in the priorityinformation in accordance with a predetermined correspondence. Thepriority information includes a Quality of Service (QoS) priority for atraffic type, a priority of a channel, a priority of a signal, and/or apriority of a logical channel.

Optionally, the method further includes, subsequent to determining thecorresponding LBT mechanism, LBT mechanism parameter set or category ofLBT mechanism parameter set in accordance with the predeterminedcorrespondence: determining more specific parameters for the LBTmechanism based on the related indication information.

Optionally, the method further includes, when performingcontention-based channel access based on the determined LBT mechanismand/or LBT mechanism parameter set: selecting, when the contention-basedaccess has failed once, an LBT mechanism and/or an LBT mechanismparameter set corresponding to a higher priority level based on thepriority information for subsequent contention-based channel access;selecting, when the contention-based access has succeeded once, an LBTmechanism and/or an LBT mechanism parameter set corresponding to a lowerpriority level based on the priority information for subsequentcontention-based channel access; selecting, when the contention-basedaccess based on the LBT mechanism and/or LBT mechanism parameter set hasfailed for a first predetermined threshold number of times, an LBTmechanism parameter set having a smaller Contention Window (CW) sizeand/or a shorter time length of Clear Channel Assessment (CCA), or amore simplified or faster LBT mechanism for contention-based channelaccess; or selecting, when the contention-based access based on the LBTmechanism and/or LBT mechanism parameter set has succeeded for a secondpredetermined threshold number of times, an LBT mechanism parameter sethaving a larger CW size and/or a longer time length of CCA, or a morecomplicated LBT mechanism for contention-based channel access. The firstpredetermined threshold number and the second first predeterminedthreshold number are predefined, obtained based on statistics, orindicated by a base station.

Optionally, the method further includes: selecting different LBTmechanisms and/or LBT mechanism parameter sets for an initialtransmission and a retransmission.

Optionally, the operation of selecting different LBT mechanisms and/orLBT mechanism parameter sets for the initial transmission and theretransmission includes:

determining the LBT mechanism and/or LBT mechanism parameter set for theretransmission such that, when compared with the LBT mechanism and/orLBT mechanism parameter set selected for the initial transmission, adifferent LBT mechanism or the same LBT mechanism with a smallerContention Window (CW) size and/or a shorter time length of ClearChannel Assessment (CCA) is determined for the retransmission.

Optionally, for a plurality of successive uplink subframes, theoperation of determining the LBT mechanism and/or LBT mechanismparameter set includes: determining to use the same LBT mechanism or LBTmechanism parameter set or different LBT mechanisms or LBT mechanismparameter sets for the respective uplink subframes.

Optionally, for same-carrier scheduling and for the plurality ofsuccessive uplink subframes, the operation of determining to usedifferent LBT mechanisms or LBT mechanism parameter sets for therespective uplink subframes includes: determining, before the firstuplink subframe is transmitted, to use a fast LBT mechanism and LBTmechanism parameter set for fast contention-based channel access; anddetermining, for each of subsequent uplink subframes, to use a fasterLBT mechanism and LBT mechanism parameter set than the LBT mechanism and

LBT mechanism parameter set used for the previous uplink subframe, forfast contention-based channel access. The fast LBT mechanism or LBTmechanism parameter set determined for the first uplink subframe isconfigured with a number of Orthogonal Frequency Division Multiplexing(OFDM) symbols.

Optionally, the method further includes, for same-carrier scheduling,when it is determined, before the first uplink subframe is transmitted,to use the fast LBT mechanism and LBT mechanism parameter set for fastcontention-based channel access: determining, for each of subsequentuplink subframes, not to use any LBT mechanism and LBT mechanismparameter set for fast contention-based channel access.

Optionally, for same-carrier scheduling and for the plurality ofsuccessive uplink subframes, the operation of determining to use thesame LBT mechanism or LBT mechanism parameter set for the respectiveuplink subframes includes: determining, before the first uplink subframeis transmitted, to use a fast LBT mechanism and LBT mechanism parameterset for fast contention-based channel access; and determining, for eachof subsequent uplink subframes, to use the same LBT mechanism and LBTmechanism parameter set as the LBT mechanism and LBT mechanism parameterset used for the first uplink subframe, for fast contention-basedchannel access. The fast LBT mechanism and LBT mechanism parameter setdetermined for the first uplink subframe are configured with a number ofOrthogonal Frequency Division Multiplexing (OFDM) symbols, and the fastLBT mechanism and LBT mechanism parameter set determined for each of thesubsequent uplink subframes are configured with one OFDM symbol.

Optionally, the fast LBT mechanism and LBT mechanism parameter setinclude at least one of: an LBT Cat4 mechanism having a maximumContention Window (CW) smaller than a CW for a downlink LBT Cat4, or adefer period plus Extended Clear Channel Assessment (ECCA) process, adirect ECCA, an enhanced LBT Cat2 and an LBT Cat2.

Optionally, for cross-carrier scheduling and for the plurality ofsuccessive uplink subframes, the operation of determining to usedifferent LBT mechanisms or LBT mechanism parameter sets for therespective uplink subframes includes: determining, before the firstuplink subframe is transmitted, to use a normal LBT Cat4 mechanism whenno data is to be transmitted in downlink and uplink grant information istransmitted over a licensed carrier; and determining, for each ofsubsequent uplink subframes, to use a LBT Cat4 mechanism having asmaller Contention Window (CW) than the LBT Cat4 mechanism used for theprevious uplink subframe, or a more simplified LBT mechanism.

Optionally, the normal LBT Cat4 mechanism determined for the firstuplink subframe is configured with a number of Orthogonal FrequencyDivision Multiplexing (OFDM) symbols, and the LBT Cat4 mechanism or themore simplified LBT mechanism determined for each of the subsequentuplink frames is configured with one OFDM symbol.

Optionally, the method further includes, when all subframes are uplinksubframes: using the first uplink subframe as a position for applyingthe LBT mechanism and/or LBT mechanism parameter set before the seconduplink subframe; and using, for each of subsequent uplink subframes, thelast Orthogonal Frequency Division Multiplexing (OFDM) symbol of theprevious uplink subframe as a position for applying the LBT mechanismand/or LBT mechanism parameter set for that uplink subframe.

Optionally, the method further includes, for a plurality of successiveuplink subframes: obtaining, by the transmitting device, a position ofan uplink subframe in a transmission burst or applying the LBT mechanismand/or LBT mechanism parameter set by:

for a fixed frame structure:

applying, by the transmitting device, the LBT mechanism and/or LBTmechanism parameter set based on a position of a subframe in which it isscheduled, in accordance with a predefined rule, or

for a flexible uplink/downlink subframe structure:

notifying, by a base station, to the transmitting device explicitly viaan indication message whether a scheduled subframe is the first subframeor a subframe that is a particular number of subframes behind the firstsubframe, or

indicating, by the base station, to the transmitting device via dynamicDownlink Control Information (DCI) the LBT mechanism and/or LBTmechanism parameter set to be applied on the scheduled subframe.

Optionally, the method further includes, when there is a plurality ofdifferent priority levels in a burst transmitted from a transmitteddevice: performing contention-based channel access in accordance with apredetermined LBT policy.

Optionally, the LBT mechanism or LBT mechanism parameter set is obtainedby one of: determining the LBT mechanism or LBT mechanism parameter setbased on information on a subframe in which a User Equipment (UE) isscheduled, determining the LBT mechanism or

LBT mechanism parameter set based on Downlink Control Information (DCI)signaling transmitted from a base station to the UE, or determining theLBT mechanism or LBT mechanism parameter set based on higher layer RadioResource Control (RRC) signaling.

Optionally, the information on the subframe in which the UE is scheduledis determined based on physical layer DCI signaling.

Optionally, for a plurality of uplink subframes or when a plurality ofsuccessive subframes is scheduled:

an LBT Cat4 is applied on the first uplink subframe and an LBT Cat2 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat2 is applied on the first uplink subframe and the LBT Cat2 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat4 is applied on the first uplink subframe and the LBT Cat4 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat4 is applied on the first uplink subframe and, for each of aplurality of subsequent uplink subframes, a smaller Contention Window(CW) is applied than the previous subframe,

the LBT Cat4 is applied on the first uplink subframe and no LBT isapplied on a plurality of subsequent uplink subframes, or

the LBT Cat2 is applied on the first uplink subframe and no LBT isapplied on a plurality of subsequent uplink subframes.

Optionally, for a plurality of uplink subframes or when a plurality ofsuccessive subframes is scheduled:

when an LBT has succeeded on an uplink subframe, no LBT is applied onsubsequent uplink subframes,

when an LBT has succeeded on an uplink subframe, an LBT is applied onsubsequent uplink subframes in accordance with an LBT mechanism or LBTmechanism parameter set signaled by a base station,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with the same LBT mechanism or LBTmechanism parameter set as the one applied on that uplink subframe,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with an LBT mechanism or LBTmechanism parameter set configured by the base station,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with a preconfigured LBT mechanism orLBT mechanism parameter set, or

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with a default LBT mechanism or LBTmechanism parameter set.

Optionally, the method further includes, when a User Equipment (UE) hasfailed successively for a number of times in accessing a channel inaccordance with a configured LBT mechanism or LBT mechanism parameterset: adjusting an LBT priority, the LBT mechanism or the LBT mechanismparameter set based on one of:

an indication signaled by a base station,

a measurement of feedback information,

a measurement of interference condition, or

a priority of at least one of: a transmitted channel, a transmittedsignal, a transmitted logical channel, or a type of transmitted traffic.

Optionally, an Information Element (IE) field for indicating the LBTmechanism or LBT mechanism parameter set is added in the physical layerDCI signaling or the higher layer RRC signaling. The IE field uses nbits, where n is an integer larger than or equal to 1.

In another aspect, an apparatus for determining a Listen Before Talk(LBT) mode is provided. The apparatus includes at least: a determiningunit configured to determining an LBT mechanism and/or an LBT mechanismparameter set based on related indication information and/or priorityinformation and/or measurement information.

Optionally, the apparatus further includes: a feedback unit configuredto transmit the determined LBT mechanism and/or LBT mechanism parameterset to a transmitting device, so as to cause the transmitting device toperform contention-based channel access based on the determined LBTmechanism and/or LBT mechanism parameter set.

Optionally, the LBT mechanism includes an LBT mechanism without randomback-off and an LBT mechanism with random back-off.

Optionally, the LBT mechanism parameter set includes: when the LBTmechanism is an LBT Cat4 mechanism, at least one of: a minimum CW; amaximum CW; and a component n of a defer period, for the LBT Cat4mechanism; or when the LBT mechanism is an LBT Cat2 mechanism, a timelength of a Clear Channel Assessment (CCA) for the LBT Cat2 mechanism.

Optionally, when the LBT mechanism is the LBT Cat4 mechanism, themechanism parameter set further includes: a time length of a first CCA.

Optionally, the apparatus further includes: a category determining unitconfigured to, when the LBT mechanism is an LBT Cat4 mechanism: dividethe LBT mechanism parameter set into respective categories depending ondifferent values of the maximum CW and the minimum CW and/or a size ofthe component n in the defer period in the parameter set for the LBTCat4. The respective categories of the LBT mechanism parameter set canhave their respective CW intervals, corresponding to their respectivemaximum CWs and minimum CWs, partially overlapping or not overlappingeach other. The category determining unit is configured to, when the LBTmechanism is an LBT Cat2 mechanism: divide the LBT mechanism parameterset into respective categories depending on different time lengths ofCCA for the LBT Cat2, or when the LBT mechanism includes the LBT Cat2and the LBT Cat4: divide the LBT mechanism parameter set into respectivecategories depending on different time lengths of CCA, sizes of CWsand/or components n in the defer period.

Optionally, the determining unit is configured to:

when the related indication information is a size of data packet to betransmitted:

preconfigure a set of sizes for data to be transmitted corresponding torespective LBT mechanisms and/or LBT mechanism parameter sets; and

select the LBT mechanism and/or LBT mechanism parameter setcorresponding to the size of data to be transmitted,

when the switching related information is a number of successivescheduled subframes:

preconfigure a set of numbers of successive scheduled subframescorresponding to the respective LBT mechanisms and/or LBT mechanismparameter sets; and

select the LBT mechanism and/or LBT mechanism parameter setcorresponding to the number of successive scheduled subframes,

when the switching related information is one or more bits configured inDownlink Control Information (DCI) signaling:

preconfigure a set of bit information and/or numbers of bits configuredin the DCI signaling corresponding to the respective LBT mechanismsand/or LBT mechanism parameter sets; and

select the LBT mechanism and/or LBT mechanism parameter setcorresponding to the bit information and/or the number of bitsconfigured in the DCI signaling for contention-based channel access,

when the switching related information is a broadcast scheme:

determine the LBT mechanism and/or LBT mechanism parameter set based onan identity in an LBT list set, a category of an LBT mechanism parameterset, an LBT mechanism and/or an LBT mechanism parameter set broadcastedto a transmitting device,

when the switching related information is a time-domain length of a gapbetween an uplink burst and a downlink burst:

preconfigure a set of time-domain lengths for the gaps corresponding tothe respective LBT mechanisms and/or LBT mechanism parameter sets; and

determine the LBT mechanism and/or LBT mechanism parameter setcorresponding to the time-domain length of the gap between the uplinkburst and the downlink burst,

when the switching related information is an identity in an LBT listsignaled from a base station:

preconfigure an information list of LBT mechanisms for switching, to beshared between that transmitting device and the base station; and

determine, by the transmitting device, the LBT mechanism and/or LBTmechanism parameter set based on information indicated by the basestation via the list,

when the related indication information is a position of a scheduledsubframe in a transmission burst or in successive uplink subframes:

preconfigure positions of the scheduled subframe in the transmissionburst or positions of the scheduled subframe in the successive uplinksubframes corresponding to respective LBT mechanisms and/or LBTmechanism parameter sets; and

determine the LBT mechanism and/or LBT mechanism parameter set based onthe position of the scheduled subframe in the transmission burst or inthe successive uplink subframes, and

when the related indication information is a carrier scenario fortransmission of a scheduling instruction:

determine the LBT mechanism and/or LBT mechanism parameter set based onsame-carrier scheduling or cross-carrier scheduling.

Optionally, the apparatus further includes: a contention processing unitconfigured to, when the switching related information is a time-domainlength of a gap between an uplink burst and a downlink burst:preconfigure a set of time-domain lengths for the gaps corresponding torespective LBT mechanisms and/or LBT mechanism parameter sets; anddetermine to apply no LBT mechanism and/or LBT mechanism parameter setwhen the time-domain length of the gap between the uplink burst and thedownlink burst is smaller than a predetermined threshold.

Optionally, the determining unit is configured to determine the LBTmechanism based on the related indication information, and thendetermine the LBT mechanism parameter set corresponding to the LBTmechanism based on different priority levels in the priorityinformation.

Optionally, the determining unit is configured to, after determining theLBT mechanism based on the related indication information: determine acorresponding LBT mechanism, LBT mechanism parameter set or category ofLBT mechanism parameter set based on different priorities contained inthe priority information in accordance with a predeterminedcorrespondence. The priority information includes a Quality of Service(QoS) priority for a traffic type, a priority of a channel, a priorityof a signal, a priority of a logical channel, and/or the priorities ofthe channel, signal and logical channel.

Optionally, the apparatus further includes: an adjusting unit configuredto, after the determining unit has determined the corresponding LBTmechanism, LBT mechanism parameter set or category of LBT mechanismparameter set in accordance with the predetermined correspondence:determine more specific parameters for the LBT mechanism based on therelated indication information.

Optionally, the apparatus further includes: an adjustment processingunit configured to, when performing contention-based channel accessbased on the determined LBT mechanism and/or LBT mechanism parameterset: select, when the contention-based access has failed once, an LBTmechanism and/or an LBT mechanism parameter set corresponding to ahigher priority level based on the priority information for subsequentcontention-based channel access; select, when the contention-basedaccess has succeeded once, an LBT mechanism and/or an LBT mechanismparameter set corresponding to a lower priority level based on thepriority information for subsequent contention-based channel access;select, when the contention-based access based on the LBT mechanismand/or LBT mechanism parameter set has failed for a first predeterminedthreshold number of times, an LBT mechanism parameter set having asmaller Contention Window (CW) size and/or a shorter time length ofClear Channel Assessment (CCA), or a more simplified or faster LBTmechanism for contention-based channel access; or select, when thecontention-based access based on the LBT mechanism and/or LBT mechanismparameter set has succeeded for a second predetermined threshold numberof times, an LBT mechanism parameter set having a larger CW size and/ora longer time length of CCA, or a more complicated LBT mechanism forcontention-based channel access. The first predetermined thresholdnumber and the second first predetermined threshold number arepredefined, obtained based on statistics, or indicated by a basestation.

Optionally, the apparatus further includes: a retransmission adjustingunit configured to adjust an LBT mechanism and/or an LBT mechanismparameter set to a retransmission of data to be transmitted, such thatdifferent LBT mechanisms and/or LBT mechanism parameter sets aredetermined for an initial transmission and the retransmission.

Optionally, the retransmission adjusting unit is configured to:determine the LBT mechanism and/or LBT mechanism parameter set for theretransmission such that, when compared with the LBT mechanism and/orLBT mechanism parameter set selected for the initial transmission, adifferent LBT mechanism or the same LBT mechanism with a smallerContention Window (CW) size and/or a shorter time length of ClearChannel Assessment (CCA) is determined for the retransmission.

Optionally, the determining unit is further configured to, for aplurality of successive uplink subframes: determine to use the same LBTmechanism or LBT mechanism parameter set or different LBT mechanisms orLBT mechanism parameter sets for the respective uplink subframes.

Optionally, the determining unit is further configured to, forsame-carrier scheduling and for a plurality of successive uplinksubframes: determine, before the first uplink subframe is transmitted,to use a fast LBT mechanism and LBT mechanism parameter set for fastcontention-based channel access; and determine, for each of subsequentuplink subframes, to use a faster LBT mechanism and LBT mechanismparameter set than the LBT mechanism and LBT mechanism parameter setused for the previous uplink subframe, for fast contention-based channelaccess. The fast LBT mechanism or LBT mechanism parameter set determinedfor the first uplink subframe is configured with a number of OrthogonalFrequency Division Multiplexing (OFDM) symbols.

Optionally, the determining unit is further configured to, forsame-carrier scheduling: determine, before the first uplink subframe istransmitted, to use a fast LBT mechanism and LBT mechanism parameter setfor fast contention-based channel access; and determine, for each ofsubsequent uplink subframes, not to use any LBT mechanism and LBTmechanism parameter set for fast contention-based channel access.

Optionally, the determining unit is further configured to, forsame-carrier scheduling and for a plurality of successive uplinksubframes: determine, before the first uplink subframe is transmitted,to use a fast LBT mechanism and LBT mechanism parameter set for fastcontention-based channel access; and determine, for each of subsequentuplink subframes, to use an LBT mechanism and an LBT mechanism parameterset having the same speed as the LBT mechanism and LBT mechanismparameter set used for the first uplink subframe, for fastcontention-based channel access. The fast LBT mechanism and LBTmechanism parameter set determined for the first uplink subframe areconfigured with a number of Orthogonal Frequency Division

Multiplexing (OFDM) symbols, and the fast LBT mechanism and LBTmechanism parameter set determined for each of the subsequent uplinksubframes are configured with one OFDM symbol.

Optionally, the determining unit is further configured to, forcross-carrier scheduling and for a plurality of successive uplinksubframes: determine, before the first uplink subframe is transmitted,to use an LBT Cat4 mechanism when no data is to be transmitted indownlink and uplink grant information is transmitted over a licensedcarrier; and determine, for each of subsequent uplink subframes, to usea LBT Cat4 mechanism having a smaller Contention Window (CW) than theLBT Cat4 mechanism used for the previous uplink subframe, or a moresimplified LBT mechanism.

Optionally, the determining unit is further configured to, forcross-carrier scheduling: determine, before the first uplink subframe istransmitted, to use an LBT Cat4 mechanism when no data is to betransmitted in downlink and uplink grant information is transmitted overa licensed carrier; and determine, for each of subsequent uplinksubframes, to apply no LBT mechanism and/or LBT mechanism parameter setfor fast contention-based channel access.

Optionally, the determining unit is further configured to, forcross-carrier scheduling and for a plurality of successive uplinksubframes: determine, before the first uplink subframe is transmitted,to use an LBT Cat4 mechanism when no data is to be transmitted indownlink and uplink grant information is transmitted over a licensedcarrier; and determine, for each of subsequent uplink subframes, to usea LBT Cat4 mechanism having a smaller Contention Window (CW) than theLBT Cat4 mechanism used for the previous uplink subframe, or a moresimplified LBT mechanism. The LBT Cat4 mechanism determined for thefirst uplink subframe is configured with a number of OrthogonalFrequency Division Multiplexing (OFDM) symbols, and the LBT Cat4mechanism or the more simplified LBT mechanism determined for each ofthe subsequent uplink subframes is configured with one OFDM symbol.

Optionally, the apparatus further includes a position determining unitconfigured to, for a plurality of successive uplink subframes: using thefirst uplink subframe as a position for applying the LBT mechanismand/or LBT mechanism parameter set before the second uplink subframe;and using, for each of subsequent uplink subframes, the last OrthogonalFrequency Division Multiplexing (OFDM) symbol of the previous uplinksubframe as a position for applying the LBT mechanism and/or LBTmechanism parameter set for that uplink subframe.

Optionally, the apparatus further includes an obtaining unit configuredto obtain a position of an uplink subframe in a transmission burst orapply the LBT mechanism and/or LBT mechanism parameter set by:

for a fixed frame structure:

applying, by the transmitting device, the LBT mechanism and/or LBTmechanism parameter set based on a position of a subframe in which it isscheduled, in accordance with a predefined rule, or

for a flexible uplink/downlink subframe structure:

notifying, by a base station, to the transmitting device explicitly viaan indication message whether a scheduled subframe is the first subframeor a subframe that is a particular number of subframes behind the firstsubframe, or

indicating, by the base station, to the transmitting device via dynamicDownlink Control Information (DCI) the LBT mechanism and/or LBTmechanism parameter set to be applied on the scheduled subframe.

Optionally, the apparatus further includes a priority policy unitconfigured to, when there is a plurality of different priority levels ina burst transmitted from a transmitted device:

determine the LBT mechanism and/or LBT mechanism parameter set inaccordance with a predetermined priority policy.

Optionally, the LBT mechanism or LBT mechanism parameter set is obtainedby one of: determining the LBT mechanism or LBT mechanism parameter setbased on information on a subframe in which a User Equipment (UE) isscheduled, determining the LBT mechanism or

LBT mechanism parameter set based on Downlink Control Information (DCI)signaling transmitted from a base station to the UE, or determining theLBT mechanism or LBT mechanism parameter set based on higher layer RadioResource Control (RRC) signaling.

Optionally, the information on the subframe in which the UE is scheduledis determined based on physical layer DCI signaling.

Optionally, for a plurality of uplink subframes or when a plurality ofsuccessive subframes is scheduled:

an LBT Cat4 is applied on the first uplink subframe and an LBT Cat2 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat2 is applied on the first uplink subframe and the LBT Cat2 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat4 is applied on the first uplink subframe and the LBT Cat4 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat4 is applied on the first uplink subframe and, for each of aplurality of subsequent uplink subframes, a smaller Contention Window(CW) is applied than the previous subframe,

the LBT Cat4 is applied on the first uplink subframe and no LBT isapplied on a plurality of subsequent uplink subframes, or

the LBT Cat2 is applied on the first uplink subframe and no LBT isapplied on a plurality of subsequent uplink subframes.

Optionally, for a plurality of uplink subframes or when a plurality ofsuccessive subframes is scheduled:

when an LBT has succeeded on an uplink subframe, no LBT is applied onsubsequent uplink subframes,

when an LBT has succeeded on an uplink subframe, an LBT is applied onsubsequent uplink subframes in accordance with an LBT mechanism or LBTmechanism parameter set signaled by a base station,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with the same LBT mechanism or LBTmechanism parameter set as the one applied on that uplink subframe,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with an LBT mechanism or LBTmechanism parameter set configured by the base station,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with a preconfigured LBT mechanism orLBT mechanism parameter set, or

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with a default LBT mechanism or LBTmechanism parameter set.

Optionally, when a User Equipment (UE) has failed successively for anumber of times in accessing a channel in accordance with a configuredLBT mechanism or LBT mechanism parameter set, an LBT priority, the LBTmechanism or the LBT mechanism parameter set is adjusted based on oneof:

an indication signaled by a base station,

a measurement of feedback information,

a measurement of interference condition, or

a priority of at least one of: a transmitted channel, a transmittedsignal, a transmitted logical channel, or a type of transmitted traffic.

Optionally, an Information Element (IE) field for indicating the LBTmechanism or LBT mechanism parameter set is added in the physical layerDCI signaling or the higher layer RRC signaling. The IE field uses nbits, where n is an integer larger than or equal to 1.

With the solutions according to the embodiments of the presentdisclosure, an LBT mechanism and/or an LBT mechanism parameter set canbe determined based on related indication information and/or priorityinformation and/or measurement information. A transmitting device canperform contention-based channel access based on the determined LBTmechanism and/or LBT mechanism parameter set. With the solutionsaccording to the embodiments of the present disclosure, an LBT mode canbe determined. With the selection of the LBT mode, it is possible toavoid waste of channel resources and indication information due to animproper LBT mode, thereby improving an efficiency of contention-basedchannel access.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure can be further understood with reference to thefigures described below, which constitute a part of the presentdisclosure. The figures and the illustrative embodiments of the presentdisclosure are provided for explaining, rather than limiting, thepresent disclosure. In the figures:

FIG. 1 is a flowchart illustrating a method for determining an LBT modeaccording to an embodiment of the present disclosure;

FIG. 2 is a block diagram showing a structure of an apparatus fordetermining an LBT mode according to an embodiment of the presentdisclosure; and

FIG. 3 is a schematic diagram showing a position of an area in which anLBT mechanism and/or an LBT mechanism parameter set is applied accordingto a sixth embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following, the embodiments of the present disclosure will bedescribed in detail with reference to the figures, such that theobjects, solutions and advantages of the present disclosure will becomemore apparent. It is to be noted that the embodiments, and the featuresthereof, can be combined with each other, provided that they do notconflict.

FIG. 1 is a flowchart illustrating a method for LBT mode switchingaccording to an embodiment of the present disclosure. As shown in FIG.1, the method includes the following steps.

At step 100, an LBT mechanism and/or an LBT mechanism parameter set isdetermined based on related indication information and/or priorityinformation and/or measurement information.

It is to be noted that the LBT mechanism and/or LBT mechanism parameterset can be determined by a transmitted device or a base station. Whenthe determination is made by the base station, the determined LBTmechanism and/or LBT mechanism parameter set needs to be transmitted tothe transmitting device, such that the transmitting device can obtainthe LBT mechanism and/or LBT mechanism parameter for use incontention-based channel access.

In this step, the related indication information can include: a size ofdata packet to be transmitted, a number of successive scheduledsubframes, one or more bits configured in physical Downlink ControlInformation (DCI) signaling, a broadcast scheme, a time-domain length ofa gap between an uplink transmission burst and a downlink transmissionburst, an identity in an LBT list signaled from a base station, aposition of a scheduled subframe in a transmission burst or insuccessive uplink subframes, a length of one transmission burst, and/ora carrier scenario for transmission of a scheduling instruction.

It is to be noted that, when the related indication information includesmore than one indication, the LBT mechanism and/or LBT mechanismparameter set can be selected as desired. For example, when the relatedindication information indicates the size of data packet to betransmitted and the number of successive scheduled subframes, the LBTmechanism can be determined based on the size of data packet to betransmitted, and the parameters set associated with the determined LBTmechanism can be selected based on the number of successive scheduledsubframes. This may depend on actual implementations.

The priority information can include: a Quality of Service (QoS)priority for a traffic type of data to be transmitted, or a priority ofa channel, a signal and/or a logical channel for the data to betransmitted, and/or the priorities of the channel, signal and logicalchannel.

The priority information can further include: a priority of a physicaltransmission channel, obtained by mapping a level of the priority of thelogical channel to the physical transmission channel.

The measurement can include: Channel State Information (CSI) within apredetermined time length, a Reference Signal Received Power (RSRP)within a predetermined time length, a Reference Signal Received Quality(RSRQ) within a predetermined time length, Hybrid Automatic RepeatreQuest—Acknowledge (HARQ-ACK) information, or information on a measuredinterference.

Preferably, the LBT mechanism in the embodiment of the presentdisclosure can include an LBT mechanism without random back-off and anLBT mechanism with random back-off.

Here, the LBT mechanism without random back-off can include an LBT Cat2mechanism and an enhanced LBT Cat2 mechanism.

Preferably, the LBT Cat2 mechanism can be an LBT mechanism in which onlyone

Clear Channel Assessment (CCA) is performed.

The enhanced LBT Cat2 mechanism can be an LBT mechanism in which two ormore CCAs are performed.

Further, each CCA can have a fixed or random start position.

Each CCA can have a time length of 34 microseconds (μs), 25 μs, 20 μs,16 μs, 9 μs or 4 μs.

The LBT mechanism with random back-off can include an LBT Cat4 mechanismhaving a variable Contention Window (CW) size and an LBT Cat3 mechanismhaving a fixed CW size. The LBT Cat4 mechanism can include at least oneof the following parameters: a first CCA; a defer period; a maximum CW,CWmax; a minimum CW, CWmin; and a random back-off value, N. The firstCCA can be an initial CCA.

The defer period can include defer time plus n multiplied by slot, or nmultiplied by slot plus defer time, where n is an integer in an intervalof [0, 2], slot has a time-length of 9 μs, and the defer time is 16 μs.

It is to be noted that, in a Wi-Fi system, the feedback time for one ACKor Negative ACK (NACK) is 16 μs and the length of one slot is 9 μs.

Preferably, the first CCA can have a time length of 34 μs, 25 μs, 20 μs,16 μs, 9 μs or 4 μs.

The random back-off value N can be a value selected randomly from aninterval of [0, q-1], where q is a value selected randomly from aninterval of [CWmin, CWmax].

The random back-off value N can be indicated by a base station,generated randomly or predetermined.

When the LBT mechanism and/or LBT mechanism parameter set is for anuplink channel, n is 0, 1 or 2. When the LBT mechanism and/or LBTmechanism parameter set is for a downlink channel, n is a natural numberranging from 1 to 7.

When the LBT mechanism is an LBT Cat4 mechanism, the LBT mechanismparameter set can include at least one of: a minimum CW; a maximum CW;and a component n of a defer period for the LBT Cat4 mechanism. When theLBT mechanism is an LBT Cat2 mechanism, the LBT mechanism parameter setcan include a time length of a CCA for the LBT Cat2 mechanism.

When the LBT mechanism is the LBT Cat4 mechanism, the mechanismparameter set can further include: a time length of the first CCA.

In an embodiment of the present disclosure, when the LBT mechanism isthe LBT Cat4 mechanism, the method can further include: dividing the LBTmechanism parameter set into respective categories depending ondifferent values of the maximum CW and the minimum CW and/or a size ofthe component n in the defer period in the parameter set for the LBTCat4.

The respective categories of the LBT mechanism parameter set can havetheir respective CW intervals, corresponding to their respective maximumCWs and minimum CWs, partially overlapping or not overlapping eachother.

In an embodiment of the present disclosure, when the LBT mechanism isthe LBT Cat2 mechanism, the method can further include: dividing the LBTmechanism parameter set into respective categories depending ondifferent time lengths of CCA for the LBT Cat2.

In an embodiment of the present disclosure, when the LBT mechanismincludes the LBT Cat2 and the LBT Cat4, the method can further include:dividing the LBT mechanism parameter set into respective categoriesdepending on different time lengths of CCA, sizes of CWs and/orcomponents n in the defer period.

The respective categories of the LBT mechanism parameter set are basedon priorities, predefined, divided based on values of available maximumCWs, divided based on time lengths of CCA, indicated by a base station,or indicated dynamically in DCI.

It is to be noted that the respective categories can be predefined bythose skilled in the art based on an empirical value. The respectivecategories being divided based on values of available maximum CWsbelongs to a common practice in the art and further details thereof willbe omitted here.

When the related indication information is the size of data packet to betransmitted, the operation of determining the LBT mechanism and/or LBTmechanism parameter set based on the related indication information caninclude: preconfiguring a set of sizes for data to be transmittedcorresponding to respective LBT mechanisms and/or LBT mechanismparameter sets; and selecting the LBT mechanism and/or LBT mechanismparameter set corresponding to the size of data packet to betransmitted.

When the switching related information is the number of successivescheduled subframes, the operation of determining the LBT mechanismand/or LBT mechanism parameter set based on the related indicationinformation can include: preconfiguring a set of numbers of successivescheduled subframes corresponding to the respective LBT mechanismsand/or LBT mechanism parameter sets; and selecting the LBT mechanismand/or LBT mechanism parameter set corresponding to the number ofsuccessive scheduled subframes.

When the switching related information is the one or more bitsconfigured in Downlink Control Information (DCI) signaling, theoperation of determining the LBT mechanism and/or LBT mechanismparameter set based on the related indication information can include:preconfiguring a set of bit information and/or numbers of bitsconfigured in the DCI signaling corresponding to the respective LBTmechanisms and/or LBT mechanism parameter sets; and selecting the LBTmechanism and/or LBT mechanism parameter set corresponding to the bitinformation and/or the number of bits configured in the DCI signalingfor contention-based channel access.

When the switching related information is the broadcast scheme, theoperation of determining the LBT mechanism and/or LBT mechanismparameter set based on the related indication information can include:determining the LBT mechanism and/or LBT mechanism parameter set basedon an identity in an LBT list set, a category of an LBT mechanismparameter set, an LBT mechanism and/or an LBT mechanism parameter setbroadcasted to a transmitting device.

When the switching related information is the time-domain length of thegap between the uplink burst and the downlink burst, the operation ofdetermining the LBT mechanism and/or LBT mechanism parameter set basedon the related indication information can include: preconfiguring a setof time-domain lengths for gaps corresponding to the respective LBTmechanisms and/or LBT mechanism parameter sets; and determining the LBTmechanism and/or LBT mechanism parameter set corresponding to thetime-domain length of the gap between the uplink burst and the downlinkburst.

When the switching related information is the identity in an LBT listsignaled from a base station, the operation of determining the LBTmechanism and/or LBT mechanism parameter set based on the relatedindication information can include: preconfiguring an information listof LBT mechanisms for switching, to be shared between that transmittingdevice and the base station; and determining, by the transmittingdevice, the LBT mechanism and/or LBT mechanism parameter set based on anidentity in the information list as indicated or broadcasted by the basestation.

When the related indication information is the position of the scheduledsubframe in the transmission burst or in the successive uplinksubframes, the operation of determining the LBT mechanism and/or LBTmechanism parameter set based on the related indication information caninclude: preconfiguring positions of the scheduled subframe in thetransmission burst or positions of the scheduled subframe in thesuccessive uplink subframes corresponding to respective LBT mechanismsand/or LBT mechanism parameter sets; and determining the LBT mechanismand/or LBT mechanism parameter set based on the position of thescheduled subframe in the transmission burst or in the successive uplinksubframes.

When the related indication information is the carrier scenario fortransmission of the scheduling instruction, the operation of determiningthe LBT mechanism and/or LBT mechanism parameter set based on therelated indication information can include: determining the LBTmechanism and/or LBT mechanism parameter set based on same-carrierscheduling or cross-carrier scheduling.

In an embodiment of the present disclosure, when the switching relatedinformation is the time-domain length of the gap between the uplinkburst and the downlink burst, the method can further include:preconfiguring a set of time-domain lengths for the gaps correspondingto respective LBT mechanisms and/or LBT mechanism parameter sets; anddetermining to apply no LBT mechanism and/or LBT mechanism parameter setwhen the time-domain length of the gap between the uplink burst and thedownlink burst is smaller than a predetermined threshold.

It is to be noted that the predefined threshold can be 16 μs or 25 μs.

The operation of determining the LBT mechanism and/or LBT mechanismparameter set based on the related indication information and thepriority information can include: determining the LBT mechanism based onthe related indication information, and then determining the LBTmechanism parameter set corresponding to the LBT mechanism based ondifferent priority levels in the priority information.

The operation of determining the LBT mechanism parameter setcorresponding to the LBT mechanism based on different priority levels inthe priority information can include: determining a corresponding LBTmechanism, LBT mechanism parameter set or category of LBT mechanismparameter set based on different priorities contained in the priorityinformation in accordance with a predetermined correspondence. Thepriority information includes a QoS priority for a traffic type, apriority of a channel, a priority of a signal, and/or a priority of alogical channel.

In an embodiment of the present disclosure, the method can furtherinclude, subsequent to determining the corresponding LBT mechanism, LBTmechanism parameter set or category of LBT mechanism parameter set inaccordance with the predetermined correspondence: determining morespecific parameters for the LBT mechanism based on the relatedindication information.

It is to be noted that the operation of determining the more specificparameters can include: after the LBT mechanism to be used has beendetermined, further determining what LBT parameters are to be used indifferent situations in the LBT mechanism based on the relatedindication information. For example, when an LBT Cat4 has beendetermined, specifics of the LBT Cat4 can be determined based on theindex of the scheduled subframe in the related indication information.For example, the LBT Cat4 can be further determined to have CWmin of 1and CWmax of 3.

Of course, when the LBT has failed for a number of times or hassucceeded in accordance with the LBT mechanism or LBT mechanismparameter set at the priority level of 3, the LBT mechanism or parameterset can be further adjusted based on a measurement of feedbackinformation, or the LBT parameter can be selected further in combinationof the position of the scheduled subframe.

At step 101, the transmitting device performs contention-based channelaccess based on the determined LBT mechanism and/or LBT mechanismparameter set.

In an embodiment of the present disclosure, when performingcontention-based channel access based on the determined LBT mechanismand/or LBT mechanism parameter set, the method can further include:

selecting, when the contention-based access has failed once, an LBTmechanism and/or an LBT mechanism parameter set corresponding to ahigher priority level based on the priority information for subsequentcontention-based channel access;

selecting, when the contention-based access has succeeded once, an LBTmechanism and/or an LBT mechanism parameter set corresponding to a lowerpriority level based on the priority information for subsequentcontention-based channel access;

(It is to be noted here that, in general, using a higher or lowerpriority level for a failed or succeeded contention-based access meansusing a priority level that is one level lower than the succeededcontention-based access or one level higher than the failedcontention-based access.)

selecting, when the contention-based access based on the LBT mechanismand/or LBT mechanism parameter set has failed for a first predeterminedthreshold number of times, an LBT mechanism parameter set having asmaller Contention Window (CW) size and/or a shorter time length ofClear Channel Assessment (CCA), or a more simplified LBT mechanism forcontention-based channel access; or

(It is to be note here that the more simplified LBT mechanism is anempirical concept used by those skilled in the art. For example, the LBTCat2 is a more simplified mechanism than the LBT Cat4. As anotherexample, when the fast LBT mechanisms are used, the LBT mechanisms, in adescending order of simplification, can be: the LBT Cat2 (the mostsimplified), the enhanced LBT Cat2, the ECCA process, the defer periodplus ECCA process, and the first CCA plus defer period and ECCAprocess.)

selecting, when the contention-based access based on the LBT mechanismand/or LBT mechanism parameter set has succeeded for a secondpredetermined threshold number of times, an LBT mechanism parameter sethaving a larger CW size and/or a longer time length of CCA, or a morecomplicated LBT mechanism for contention-based channel access.

(It is to be noted here that the concept of “more complicated” isopposite to the concept of “more simplified” and can be deduced from thelatter. For example, the enhanced LBT Cat2 is more complicated than theLBT Cat2.)

The first predetermined threshold number and the second firstpredetermined threshold number can be predefined, obtained based onstatistics, or indicated by a base station.

In an embodiment of the present disclosure, the method can furtherinclude: selecting different LBT mechanisms and/or LBT mechanismparameter sets for an initial transmission and a retransmission.

The operation of selecting different LBT mechanisms and/or LBT mechanismparameter sets for the initial transmission and the retransmission caninclude: determining the LBT mechanism and/or LBT mechanism parameterset for the retransmission such that, when compared with the LBTmechanism and/or LBT mechanism parameter set selected for the initialtransmission, a different LBT mechanism or the same LBT mechanism with asmaller CW size and/or a shorter time length of CCA is determined forthe retransmission.

When the data to be transmitted includes a plurality of successiveuplink subframes, the operation of determining the LBT mechanism and/orLBT mechanism parameter set can include, for the plurality of successiveuplink subframes: determining to use the same LBT mechanism or LBTmechanism parameter set or different LBT mechanisms or LBT mechanismparameter sets for the respective uplink subframes.

In particular, for same-carrier scheduling and for the plurality ofsuccessive uplink subframes, the operation of determining to usedifferent LBT mechanisms or LBT mechanism parameter sets for therespective uplink subframes can include: determining, before the firstuplink subframe is transmitted, to use a fast LBT mechanism and LBTmechanism parameter set for fast contention-based channel access; anddetermining, for each of subsequent uplink subframes, to use a fasterLBT mechanism and LBT mechanism parameter set than the LBT mechanism andLBT mechanism parameter set used for the previous uplink subframe, forfast contention-based channel access. The fast LBT mechanism or LBTmechanism parameter set determined for the first uplink subframe isconfigured with a number of Orthogonal Frequency Division Multiplexing(OFDM) symbols. Typically, the term “a number of” means two or more.

In an embodiment of the present disclosure, for same-carrier scheduling,the method can further include, when it is determined, before the firstuplink subframe is transmitted, to use the fast LBT mechanism and LBTmechanism parameter set for fast contention-based channel access:determining, for each of subsequent uplink subframes, not to use any LBTmechanism and LBT mechanism parameter set for fast contention-basedchannel access.

For same-carrier scheduling and for the plurality of successive uplinksubframes, the operation of determining to use the same LBT mechanism orLBT mechanism parameter set for the respective uplink subframes caninclude: determining, before the first uplink subframe is transmitted,to use a fast LBT mechanism and LBT mechanism parameter set for fastcontention-based channel access; and determining, for each of subsequentuplink subframes, to use the same LBT mechanism and LBT mechanismparameter set as the LBT mechanism and LBT mechanism parameter set usedfor the first uplink subframe, for fast contention-based channel access.The fast LBT mechanism and LBT mechanism parameter set determined forthe first uplink subframe are configured with a number of OFDM symbols,and the fast LBT mechanism and LBT mechanism parameter set determinedfor each of the subsequent uplink subframes are configured with one OFDMsymbol.

Here, the fast LBT mechanism and LBT mechanism parameter set include atleast one of: an LBT Cat4 mechanism having a maximum CW smaller than aCW for a downlink LBT Cat4, or a defer period plus Extended ClearChannel Assessment (ECCA) process, a direct ECCA, an enhanced LBT Cat2and an LBT Cat2.

It is to be noted that, in the defer period+ECCA process, a CCA having atime length equal to the defer period is performed first and, if thechannel is assessed to be busy in the defer period, an ECCA randomback-off is applied. Here, the ECCA process is to perform a CCA having arandom back-off value of N slots. Only when the channel is assessed tobe idle in one slot, the CCA in the next slot can be performed. When thechannel is assessed to be idle in one slot, the random back-off value Nis decremented by 1. If the channel is busy, the CCA in the defer periodis performed. Here, if the channel is assessed to be idle in the deferperiod, the random back-off value N can also be decremented.

For cross-carrier scheduling and for the plurality of successive uplinksubframes, the operation of determining to use different LBT mechanismsor LBT mechanism parameter sets for the respective uplink subframes caninclude: determining, before the first uplink subframe is transmitted,to use a normal LBT Cat4 mechanism when no data is to be transmitted indownlink and uplink grant information is transmitted over a licensedcarrier; and determining, for each of subsequent uplink subframes, touse a LBT Cat4 mechanism having a smaller CW than the LBT Cat4 mechanismused for the previous uplink subframe, or a more simplified LBTmechanism.

Preferably, the LBT Cat4 mechanism determined for the first uplinksubframe can be configured with a number of OFDM symbols, and the LBTCat4 mechanism or the more simplified LBT mechanism determined for eachof the subsequent uplink frames can be configured with one OFDM symbol.

In an embodiment of the present disclosure, for cross-carrierscheduling, the method can further include: determining, before thefirst uplink subframe is transmitted, to use an LBT Cat4 mechanism whenno data is to be transmitted in downlink and uplink grant information istransmitted over a licensed carrier; and determining, for each ofsubsequent uplink subframes, to apply no LBT mechanism and/or LBTmechanism parameter set for contention-based channel access.

In an embodiment of the present disclosure, when all subframes areuplink subframes, the method can further include: using the first uplinksubframe as a position for applying the

LBT mechanism and/or LBT mechanism parameter set before the seconduplink subframe; and using, for each of subsequent uplink subframes, thelast Orthogonal Frequency Division Multiplexing (OFDM) symbol of theprevious uplink subframe as a position for applying the LBT mechanismand/or LBT mechanism parameter set for that uplink subframe.

In an embodiment of the present disclosure, the method can furtherinclude, for a plurality of successive uplink subframes: obtaining, bythe transmitting device, a position of an uplink subframe in atransmission burst or applying the LBT mechanism and/or LBT mechanismparameter set by:

for a fixed frame structure:

applying, by the transmitting device, the LBT mechanism and/or LBTmechanism parameter set based on a position of a subframe in which it isscheduled, in accordance with a predefined rule, or

for a flexible uplink/downlink subframe structure:

notifying, by a base station, to the transmitting device explicitly viaan indication message whether a scheduled subframe is the first subframeor a subframe that is a particular number of subframes behind the firstsubframe, or

indicating, by the base station, to the transmitting device via dynamicDownlink Control Information (DCI) the LBT mechanism and/or LBTmechanism parameter set to be applied on the scheduled subframe.

In an embodiment of the present disclosure, when there is a plurality ofdifferent priority levels in a burst transmitted from a transmitteddevice, the method can further include: performing contention-basedchannel access in accordance with a predetermined LBT policy.

Optionally, the LBT mechanism or LBT mechanism parameter set can beobtained by one of: determining the LBT mechanism or LBT mechanismparameter set based on information on a subframe in which a UserEquipment (UE) is scheduled, determining the LBT mechanism or LBTmechanism parameter set based on Downlink Control Information (DCI)signaling transmitted from a base station to the UE, or determining theLBT mechanism or LBT mechanism parameter set based on higher layer RadioResource Control (RRC) signaling.

Optionally, the information on the subframe in which the UE is scheduledcan be determined based on physical layer DCI signaling.

Optionally, for a plurality of uplink subframes or when a plurality ofsuccessive subframes is scheduled:

an LBT Cat4 is applied on the first uplink subframe and an LBT Cat2 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat2 is applied on the first uplink subframe and the LBT Cat2 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat4 is applied on the first uplink subframe and the LBT Cat4 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat4 is applied on the first uplink subframe and, for each of aplurality of subsequent uplink subframes, a smaller Contention Window(CW) is applied than the previous subframe,

the LBT Cat4 is applied on the first uplink subframe and no LBT isapplied on a plurality of subsequent uplink subframes, or

the LBT Cat2 is applied on the first uplink subframe and no LBT isapplied on a plurality of subsequent uplink subframes.

Optionally, for a plurality of uplink subframes or when a plurality ofsuccessive subframes is scheduled:

when an LBT has succeeded on an uplink subframe, no LBT is applied onsubsequent uplink subframes,

when an LBT has succeeded on an uplink subframe, an LBT is applied onsubsequent uplink subframes in accordance with an LBT mechanism or LBTmechanism parameter set signaled by a base station,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with the same LBT mechanism or LBTmechanism parameter set as the one applied on that uplink subframe,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with an LBT mechanism or LBTmechanism parameter set configured by the base station,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with a preconfigured LBT mechanism orLBT mechanism parameter set, or

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with a default LBT mechanism or LBTmechanism parameter set.

Optionally, when a User Equipment (UE) has failed successively for anumber of times in accessing a channel in accordance with a configuredLBT mechanism or LBT mechanism parameter set, the method can furtherinclude: adjusting an LBT priority, the LBT mechanism or the LBTmechanism parameter set based on one of:

an indication signaled by a base station,

a measurement of feedback information,

a measurement of interference condition, or

a priority of at least one of: a transmitted channel, a transmittedsignal, a transmitted logical channel, or a type of transmitted traffic.

Optionally, an Information Element (IE) field for indicating the LBTmechanism or LBT mechanism parameter set can be added in the physicallayer DCI signaling or the higher layer RRC signaling. The IE field canuse n bits, where n is an integer larger than or equal to 1.

With the method according to the embodiments of the present disclosure,an LBT mode can be determined. With the selection of the LBT mode, it ispossible to avoid waste of channel resources and indication informationdue to an improper LBT mode, thereby improving an efficiency ofcontention-based channel access.

FIG. 2 is a block diagram showing a structure of an apparatus fordetermining an LBT mode according to an embodiment of the presentdisclosure. As shown in FIG. 2, the apparatus includes at least: adetermining unit configured to determining an LBT mechanism and/or anLBT mechanism parameter set based on related indication informationand/or priority information and/or measurement information.

In an embodiment of the present disclosure, the apparatus can furtherinclude: a feedback unit configured to transmit the determined LBTmechanism and/or LBT mechanism parameter set to a transmitting device,so as to cause the transmitting device to perform contention-basedchannel access based on the determined LBT mechanism and/or LBTmechanism parameter set.

The LBT mechanism can include an LBT mechanism without random back-offand an LBT mechanism with random back-off.

When the LBT mechanism is an LBT Cat4 mechanism, the LBT mechanismparameter set can include at least one of: a minimum CW; a maximum CW;and a component n of a defer period for the LBT Cat4 mechanism. When theLBT mechanism is an LBT Cat2 mechanism, the LBT mechanism parameter setcan include a time length of a CCA for the LBT Cat2 mechanism.

When the LBT mechanism is the LBT Cat4 mechanism, the mechanismparameter set can further include: a time length of a first CCA.

In an embodiment of the present disclosure, the apparatus can furtherinclude: a category determining unit configured to, when the LBTmechanism is an LBT Cat4 mechanism: divide the LBT mechanism parameterset into respective categories depending on different values of themaximum CW and the minimum CW and/or a size of the component n in thedefer period in the parameter set for the LBT Cat4. The respectivecategories of the LBT mechanism parameter set can have their respectiveCW intervals, corresponding to their respective maximum CWs and minimumCWs, partially overlapping or not overlapping each other. The categorydetermining unit can be configured to, when the LBT mechanism is an LBTCat2 mechanism: divide the LBT mechanism parameter set into respectivecategories depending on different time lengths of CCA for the LBT Cat2,or when the LBT mechanism includes the LBT Cat2 and the LBT Cat4: dividethe LBT mechanism parameter set into respective categories depending ondifferent time lengths of CCA, sizes of CWs and/or components n in thedefer period.

The determining unit can be configured to:

when the related indication information is a size of data packet to betransmitted:

preconfigure a set of sizes for data to be transmitted corresponding torespective LBT mechanisms and/or LBT mechanism parameter sets; and

select the LBT mechanism and/or LBT mechanism parameter setcorresponding to the size of data packet to be transmitted,

when the switching related information is a number of successivescheduled subframes:

preconfigure a set of numbers of successive scheduled subframescorresponding to the respective LBT mechanisms and/or LBT mechanismparameter sets; and

select the LBT mechanism and/or LBT mechanism parameter setcorresponding to the number of successive scheduled subframes,

when the switching related information is one or more bits configured inDownlink Control Information (DCI) signaling:

preconfigure a set of bit information and/or numbers of bits configuredin the DCI signaling corresponding to the respective LBT mechanismsand/or LBT mechanism parameter sets; and

select the LBT mechanism and/or LBT mechanism parameter setcorresponding to the bit information and/or the number of bitsconfigured in the DCI signaling for contention-based channel access,

when the switching related information is a broadcast scheme:

determine the LBT mechanism and/or LBT mechanism parameter set based onan identity in an LBT list set, a category of an LBT mechanism parameterset, an LBT mechanism and/or an LBT mechanism parameter set broadcastedto a transmitting device,

when the switching related information is a time-domain length of a gapbetween an uplink burst and a downlink burst:

preconfigure a set of time-domain lengths for the gaps corresponding tothe respective LBT mechanisms and/or LBT mechanism parameter sets; and

determine the LBT mechanism and/or LBT mechanism parameter setcorresponding to the time-domain length of the gap between the uplinkburst and the downlink burst,

when the switching related information is an identity in an LBT listsignaled from a base station:

preconfigure an information list of LBT mechanisms for switching, to beshared between that transmitting device and the base station; and

determine, by the transmitting device, the LBT mechanism and/or LBTmechanism parameter set based on information indicated by the basestation via the list,

when the related indication information is a position of a scheduledsubframe in a transmission burst or in successive uplink subframes:

preconfigure positions of the scheduled subframe in the transmissionburst or positions of the scheduled subframe in the successive uplinksubframes corresponding to respective LBT mechanisms and/or LBTmechanism parameter sets; and

determine the LBT mechanism and/or LBT mechanism parameter set based onthe position of the scheduled subframe in the transmission burst or inthe successive uplink subframes, and

when the related indication information is a carrier scenario fortransmission of a scheduling instruction:

determine the LBT mechanism and/or LBT mechanism parameter set based onsame-carrier scheduling or cross-carrier scheduling.

In an embodiment of the present disclosure, the apparatus can furtherinclude: a contention processing unit configured to, when the switchingrelated information is a time-domain length of a gap between an uplinkburst and a downlink burst: preconfigure a set of time-domain lengthsfor the gaps corresponding to respective LBT mechanisms and/or LBTmechanism parameter sets; and determine to apply no LBT mechanism and/orLBT mechanism parameter set when the time-domain length of the gapbetween the uplink burst and the downlink burst is smaller than apredetermined threshold.

The determining unit can be configured to determine the LBT mechanismbased on the related indication information, and then determine the LBTmechanism parameter set corresponding to the LBT mechanism based ondifferent priority levels in the priority information.

The determining unit can be configured to, after determining the LBTmechanism based on the related indication information: determine acorresponding LBT mechanism, LBT mechanism parameter set or category ofLBT mechanism parameter set based on different priorities contained inthe priority information in accordance with a predeterminedcorrespondence. The priority information can include a QoS priority fora traffic type, a priority of a channel, a priority of a signal, apriority of a logical channel, and/or the priorities of the channel,signal and logical channel.

In an embodiment of the present disclosure, the apparatus can furtherinclude: an adjusting unit configured to, after the determining unit hasdetermined the corresponding LBT mechanism, LBT mechanism parameter setor category of LBT mechanism parameter set in accordance with thepredetermined correspondence: determine more specific parameters for theLBT mechanism based on the related indication information.

In an embodiment of the present disclosure, the apparatus can furtherinclude: an adjustment processing unit configured to, when performingcontention-based channel access based on the determined LBT mechanismand/or LBT mechanism parameter set: select, when the contention-basedaccess has failed once, an LBT mechanism and/or an LBT mechanismparameter set corresponding to a higher priority level based on thepriority information for subsequent contention-based channel access;select, when the contention-based access has succeeded once, an LBTmechanism and/or an LBT mechanism parameter set corresponding to a lowerpriority level based on the priority information for subsequentcontention-based channel access; select, when the contention-basedaccess based on the LBT mechanism and/or LBT mechanism parameter set hasfailed for a first predetermined threshold number of times, an LBTmechanism parameter set having a smaller CW size and/or a shorter timelength of CCA, or a more simplified or faster LBT mechanism forcontention-based channel access; or select, when the contention-basedaccess based on the LBT mechanism and/or LBT mechanism parameter set hassucceeded for a second predetermined threshold number of times, an LBTmechanism parameter set having a larger CW size and/or a longer timelength of CCA, or a more complicated LBT mechanism for contention-basedchannel access. The first predetermined threshold number and the secondfirst predetermined threshold number can be predefined, obtained basedon statistics, or indicated by a base station.

In an embodiment of the present disclosure, the apparatus can furtherinclude: a retransmission adjusting unit configured to adjust an LBTmechanism and/or an LBT mechanism parameter set to a retransmission ofdata to be transmitted, such that different LBT mechanisms and/or LBTmechanism parameter sets are determined for an initial transmission andthe retransmission.

The retransmission adjusting unit can be configured to: determine theLBT mechanism and/or LBT mechanism parameter set for the retransmissionsuch that, when compared with the LBT mechanism and/or LBT mechanismparameter set selected for the initial transmission, a different LBTmechanism or the same LBT mechanism with a smaller CW size and/or ashorter time length of CCA is determined for the retransmission.

The determining unit can further be configured to, for a plurality ofsuccessive uplink subframes: determine to use the same LBT mechanism orLBT mechanism parameter set or different LBT mechanisms or LBT mechanismparameter sets for the respective uplink subframes.

The determining unit can further be configured to, for same-carrierscheduling and for a plurality of successive uplink subframes:determine, before the first uplink subframe is transmitted, to use afast LBT mechanism and LBT mechanism parameter set for fastcontention-based channel access; and determine, for each of subsequentuplink subframes, to use a faster LBT mechanism and LBT mechanismparameter set than the LBT mechanism and LBT mechanism parameter setused for the previous uplink subframe, for fast contention-based channelaccess. The fast LBT mechanism or LBT mechanism parameter set determinedfor the first uplink subframe is configured with a number of OFDMsymbols.

The determining unit can further be configured to, for same-carrierscheduling:

determine, before the first uplink subframe is transmitted, to use afast LBT mechanism and LBT mechanism parameter set for fastcontention-based channel access; and determine, for each of subsequentuplink subframes, not to use any LBT mechanism and LBT mechanismparameter set for fast contention-based channel access.

The determining unit can further be configured to, for same-carrierscheduling and for a plurality of successive uplink subframes:determine, before the first uplink subframe is transmitted, to use afast LBT mechanism and LBT mechanism parameter set for fastcontention-based channel access; and determine, for each of subsequentuplink subframes, to use an LBT mechanism and an LBT mechanism parameterset having the same speed as the LBT mechanism and LBT mechanismparameter set used for the first uplink subframe, for fastcontention-based channel access. The fast LBT mechanism and LBTmechanism parameter set determined for the first uplink subframe areconfigured with a number of OFDM symbols, and the fast LBT mechanism andLBT mechanism parameter set determined for each of the subsequent uplinksubframes are configured with one OFDM symbol.

The determining unit can further be configured to, for cross-carrierscheduling and for a plurality of successive uplink subframes:determine, before the first uplink subframe is transmitted, to use anLBT Cat4 mechanism when no data is to be transmitted in downlink anduplink grant information is transmitted over a licensed carrier; anddetermine, for each of subsequent uplink subframes, to use a LBT Cat4mechanism having a smaller CW than the LBT Cat4 mechanism used for theprevious uplink subframe, or a more simplified LBT mechanism.

The determining unit can further be configured to, for cross-carrierscheduling: determine, before the first uplink subframe is transmitted,to use an LBT Cat4 mechanism when no data is to be transmitted indownlink and uplink grant information is transmitted over a licensedcarrier; and determine, for each of subsequent uplink subframes, toapply no LBT mechanism and/or LBT mechanism parameter set for fastcontention-based channel access.

The determining unit can further be configured to, for cross-carrierscheduling and for a plurality of successive uplink subframes:determine, before the first uplink subframe is transmitted, to use anLBT Cat4 mechanism when no data is to be transmitted in downlink anduplink grant information is transmitted over a licensed carrier; anddetermine, for each of subsequent uplink subframes, to use a LBT Cat4mechanism having a smaller CW than the LBT Cat4 mechanism used for theprevious uplink subframe, or a more simplified LBT mechanism. The LBTCat4 mechanism determined for the first uplink subframe is configuredwith a number of OFDM symbols, and the LBT Cat4 mechanism or the moresimplified LBT mechanism determined for each of the subsequent uplinksubframes is configured with one OFDM symbol.

In an embodiment of the present disclosure, the apparatus can furtherinclude: a position determining unit configured to, for a plurality ofsuccessive uplink subframes: using the first uplink subframe as aposition for applying the LBT mechanism and/or LBT mechanism parameterset before the second uplink subframe; and using, for each of subsequentuplink subframes, the last OFDM symbol of the previous uplink subframeas a position for applying the LBT mechanism and/or LBT mechanismparameter set for that uplink subframe.

In an embodiment of the present disclosure, the apparatus can furtherinclude: an obtaining unit configured to obtain a position of an uplinksubframe in a transmission burst or apply the LBT mechanism and/or LBTmechanism parameter set by:

for a fixed frame structure:

applying, by the transmitting device, the LBT mechanism and/or LBTmechanism parameter set based on a position of a subframe in which it isscheduled, in accordance with a predefined rule, or

for a flexible uplink/downlink subframe structure:

notifying, by a base station, to the transmitting device explicitly viaan indication message whether a scheduled subframe is the first subframeor a subframe that is a particular number of subframes behind the firstsubframe, or

indicating, by the base station, to the transmitting device via dynamicDownlink

Control Information (DCI) the LBT mechanism and/or LBT mechanismparameter set to be applied on the scheduled subframe.

In an embodiment of the present disclosure, the apparatus can furtherinclude: a priority policy unit configured to, when there is a pluralityof different priority levels in a burst transmitted from a transmitteddevice: determine the LBT mechanism and/or LBT mechanism parameter setin accordance with a predetermined priority policy.

Optionally, the LBT mechanism or LBT mechanism parameter set can beobtained by one of: determining the LBT mechanism or LBT mechanismparameter set based on information on a subframe in which a UserEquipment (UE) is scheduled, determining the LBT mechanism or LBTmechanism parameter set based on Downlink Control Information (DCI)signaling transmitted from a base station to the UE, or determining theLBT mechanism or LBT mechanism parameter set based on higher layer RadioResource Control (RRC) signaling.

Optionally, the information on the subframe in which the UE is scheduledcan be determined based on physical layer DCI signaling.

Optionally, for a plurality of uplink subframes or when a plurality ofsuccessive subframes is scheduled:

an LBT Cat4 is applied on the first uplink subframe and an LBT Cat2 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat2 is applied on the first uplink subframe and the LBT Cat2 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat4 is applied on the first uplink subframe and the LBT Cat4 isapplied on a plurality of subsequent uplink subframes,

the LBT Cat4 is applied on the first uplink subframe and, for each of aplurality of subsequent uplink subframes, a smaller Contention Window(CW) is applied than the previous subframe,

the LBT Cat4 is applied on the first uplink subframe and no LBT isapplied on a plurality of subsequent uplink subframes, or

the LBT Cat2 is applied on the first uplink subframe and no LBT isapplied on a plurality of subsequent uplink subframes.

Optionally, for a plurality of uplink subframes or when a plurality ofsuccessive subframes is scheduled:

when an LBT has succeeded on an uplink subframe, no LBT is applied onsubsequent uplink subframes,

when an LBT has succeeded on an uplink subframe, an LBT is applied onsubsequent uplink subframes in accordance with an LBT mechanism or LBTmechanism parameter set signaled by a base station,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with the same LBT mechanism or LBTmechanism parameter set as the one applied on that uplink subframe,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with an LBT mechanism or LBTmechanism parameter set configured by the base station,

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with a preconfigured LBT mechanism orLBT mechanism parameter set, or

when an LBT has failed on an uplink subframe, an LBT is applied on thenext uplink subframe in accordance with a default LBT mechanism or LBTmechanism parameter set.

Optionally, when a (UE has failed successively for a number of times inaccessing a channel in accordance with a configured LBT mechanism or LBTmechanism parameter set, an LBT priority, the LBT mechanism or the LBTmechanism parameter set can be adjusted based on one of:

an indication signaled by a base station,

a measurement of feedback information,

a measurement of interference condition, or

a priority of at least one of: a transmitted channel, a transmittedsignal, a transmitted logical channel, or a type of transmitted traffic.

Optionally, an IE field for indicating the LBT mechanism or LBTmechanism parameter set can be added in the physical layer DCI signalingor the higher layer RRC signaling. The IE field can use n bits, where nis an integer larger than or equal to 1.

It is to be noted that, in the apparatus according to the embodiments ofthe present disclosure, the respective units can be provided at the basestation or at the transmitting device, or can be standalone devicesconnected to the base station and the transmitting device, depending onactual network structures. When they are provided at separate locations,some information needs to be exchanged via network communications asestablished. Such modifications can be contemplated by those skilled inthe art without inventive efforts.

A method for LBT mode switching is provided. The method includes:determining an LBT mechanism and/or an LBT mechanism parameter set basedon related indication information and/or priority information and/ormeasurement information; and performing, by a transmitting device,contention-based channel access based on the determined LBT mechanismand/or LBT mechanism parameter set.

In the following, the method according to the embodiment of the presentdisclosure will be explained in detail with reference to specificembodiments. These embodiments are provided only for the purpose ofillustrating the embodiments of the present disclosure, rather thanlimiting the scope of the embodiments of the present disclosure.

Embodiment 1

In this embodiment, there are two types of LBT mode switching:

Type 1: switching between different LBT mechanisms, and

Type 2: switching between different LBT mechanism parameter set withinone LBT mechanism.

The LBT mechanisms include an LBT Cat2 mechanism, an LBT Cat4 mechanismand an LBT Cat3 mechanism. The LBT Cat2 mechanism is an LBT mechanismwithout random back-off. The LBT mechanism without random back-off canbe categorized into: an LBT Cat2 in which only one CCA is performed forcontention-based channel access, and an enhanced LBT Cat2 in which morethan one CCA is performed for contention-based channel access. In theLBT Cat2 mechanism, each CCA can have a time length of 34μs, 25 μs, 20μs, 16 μs, 9 μs or 4 μs. The time length of the CCA can be predefined,indicated by a base station, notified via RRC signaling, determinedbased on different QoS levels, determined based on priorities ofdifferent channels/signals/logical channels, or determined based on therelated indication information provided according to the embodiment ofthe present disclosure. Here, the term “predefined” means it isdetermined empirically by those skilled in the art. Typically, a higherQoS level (i.e., a lower priority index) corresponds to a shorter timelength of the CCA and a higher priority of channel/signal/logicalchannel corresponds to a longer time length of the CCA.

The LBT Cat4 mechanism is an LBT mechanism with random back-off having avariable CW size. The set of parameters for the LBT Cat4 mechanismincludes a first CCA; a random back-off value, N; a minimum CW, CWmin; amaximum CW, CWmax; and a defer period. The defer period consists of n by9 μs plus 16 μs or 16 μs plus n by 9 μs, where n is a natural number.

Preferably, the first CCA (e.g., the first CCA) can have a time lengthof 34 μs (16 μs+2*9 μs or 9 μs+(16 μs+16μs)), 25 μs or 9 μs. The randomback-off value N is a value in an interval of [0, q-1], where q is avalue ranging from CWmin to CWmax. For the uplink LBT Cat4 mechanism,the value of n in the defer period can be in a range of [0, 2].Optionally, the value of n can be 1 as an empirical value. Further, inorder to allow a transmitting device to access the channel fast, n canbe configured as 0. In order to align it with the time length of

Distributed Inter-Frame Spacing (DIFS) detection in the Wi-Fi system,the value of n can be 2. The LBT Cat2 mechanism is a special case of LBTCat4 when the random back-off value in the LBT Cat4 is 0.

The LBT Cat3 mechanism is an LBT mechanism with random back-off having afixed CW size. Preferably, the LBT Cat3 mechanism is a special case ofLBT Cat4 when CWmin=CWmax in the LBT Cat4.

The switching between LBT mechanism parameter sets includes switchingbetween LBT parameter sets having different time lengths of CCA ordifferent CW sizes, or between different LBT mechanisms.

Here, the switching between the above respective LBT mechanisms or LBTmechanism parameter sets can be triggered in a defined condition orsituation, including different CW sizes, different n values in the deferperiod and/or different time lengths of CCA between different parametersets.

Embodiment 2

In this embodiment, the related indication information is a size of datapacket to be transmitted. The LBT mechanism and/or LBT mechanismparameter set can be determined based on the related indicationinformation as follows.

A set of sizes for data to be transmitted corresponding to respectiveLBT mechanisms and/or LBT mechanism parameter sets can be preconfigured.The LBT mechanism and/or LBT mechanism parameter set corresponding tothe size of data packet to be transmitted falls can be selected forcontention-based channel access. In this example, the set of sizes fordata to be transmitted may include intervals: [x1, x2], [x3, x4], [x5,x6] and [x7, x8]. The respective intervals for sizes of data to betransmitted may partially overlap or not overlap each other. Typically,an interval has a minimum value smaller than or equal to a minimum valuein its previous interval, and a maximum value larger than a maximumvalue in its previous interval. This embodiment will be explained indetail with reference to an example where the size of data packet to betransmitted falls into the respective intervals for sizes of data to betransmitted.

In this embodiment, when the size (A) of data packet to be transmittedfalls into different intervals for sizes of data to be transmitted, thecorresponding LBT mechanisms and/or LBT mechanism parameter sets can beselected. When the size of data packet to be transmitted by atransmitting device (e.g., an LAA UE in this embodiment) falls into [x1,x2], the LAA UE can use the LBT Cat2 mechanism in which only one CCA isperformed before transmission. The main reason for selecting the LBTCat2 mechanism is that the data packet to be transmitted is not largeand, even if the LBT mechanism fails, there would not be a severe wasteof resources. Here, the size of data packet to be transmitted mainlyconfigured by a base station depending on the transmitting device. Inaddition, the LBT Cat2 mechanism can allow the transmitting device toperform fast contention-based channel access, so as to transmit datapackets. When the size (A) of data packet to be transmitted falls into[x3, x4], the LAA UE can use the LBT Cat2 mechanism in which two or moreCCAs are performed before transmission, so as to provide more than oneopportunity for channel access, thereby ensuring that the transmittingdevice can successfully transmit the data in the size of data packet tobe transmitted in this interval. When the size (A) of data packet to betransmitted falls into [x5, x6], the LAA UE can use the LBT Cat3mechanism before transmission. When the size (A) of data packet to betransmitted falls into [x7, x8], the LAA UE can use the LBT Cat4mechanism before transmission. In this embodiment, the LBT mechanism isselected, based on the size of data packet to be transmitted, forcontention-based channel access. When the data packet to be transmittedis large, the LBT mechanism having a long time length of CCA or a largeCW size will be selected. Different LBT mechanisms can be selectedflexibly depending on the size of data packet to be transmitted. In thisway, it is possible to ensure an efficient and fast transmission ofdata, as well as a proper utilization of resources.

In this embodiment, when the size (A) of data packet to be transmittedfalls into different intervals, different LBT mechanism parameter setscan be selected for contention-based channel access. In particular,different values of CWs in the parameter sets can be selected forcontention-based channel access. When the size (A) of data packet to betransmitted falls into [x1, x2], the LAA UE can use the LBT Cat4mechanism having the minimum CW before transmission. For example, theminimum CW, CWmin, can be 1, the maximum CW, CWmax, can be 3, and thevalue of n in the defer period can be 1 or 2. Of course, in order toprovide a faster contention-based channel access, n can be configured as0. When the size (A) of data packet to be transmitted falls into [x3,x4], the LAA UE can use the LBT Cat4 mechanism having a CW larger thanthe minimum CW before transmission, and so on. As the size of datapacket increases, the CW of the corresponding LBT Cat4 increases. Theintervals for sizes of data packet to be transmitted may partiallyoverlap or not overlap. The end point values of the intervals have anincreasing trend.

Embodiment 3

In this embodiment, the related indication information is a number ofsuccessive scheduled subframes. The LBT mechanism and/or LBT mechanismparameter set can be determined based on the related indicationinformation in a similar way that the LBT mechanism and/or LBT mechanismparameter set is determined based on the size of data packet to betransmitted.

In particular, a set of numbers of successive scheduled subframescorresponding to the respective LBT mechanisms and/or LBT mechanismparameter sets can be preconfigured. The LBT mechanism and/or LBTmechanism parameter set corresponding to the number of successivescheduled subframes falls can be selected for contention-based channelaccess. The principles associated with values and overlapping for theintervals for numbers of successive scheduled subframes are the same asthose for the intervals for sizes of data to be transmitted. In thisembodiment, it is assumed that the set of numbers of successivescheduled subframes include intervals: [m1, m2], [m3, m4], [m5, m6] and[m7, m8].

When the number (A) of successive scheduled subframes falls into [m1,m2], the LAA UE can use the LBT Cat2 mechanism in which only one CCA isperformed before transmission. When the number (A) of successivescheduled subframes falls into [m3, m4], the LAA UE can use the LBT Cat2mechanism in which two or more CCAs are performed before transmission.Similarly, when the number (A) of successive subframes in which the UEis scheduled falls into [m5, m6], the LAA UE can use the LBT Cat3mechanism before transmission. When the number (A) of successivesubframes in which the UE is scheduled into [m7, m8], the LAA UE can usethe LBT Cat4 mechanism before transmission. Here, the end point valuesof each interval can be different (i.e., for each interval, the left endpoint value can be smaller than the right end point) or the same. Thenumber of uplink transmission subframes or the length of the uplinktransmission burst can be 1 ms, 2 ms, 3 ms, 4 ms, 5 ms or larger than 5ms, depending on the specific frame structure. Preferably, m1 and/or m2can be configured as 1 ms or 2 ms. When the available uplink LBTmechanisms include the LBT Cat2 and LBT Cat4 mechanisms only, differentsizes of data packet may correspond to the LBT Cat2 and the LBT Cat4mechanisms having successively increasing CW values. That is, the LBTCat2 and the LBT Cat4 having different CW sizes correspond to differentintervals for numbers of successive scheduled subframes. Alternatively,when only the LBT Cat4 mechanism is available before uplinktransmission, the LBT mechanism parameter set can be selected by:selecting different CW sizes in the LBT mechanism parameter set based ondifferent intervals for numbers of successive scheduled subframes intowhich the number (A) of successive scheduled subframes falls. Inparticular, the LBT mode can be switched in the following manner:

When the number (A) of successive scheduled subframes falls into [m1,m2], the LAA UE can use a minimum CW (CWmin) of 1 and a maximum CW(CWmax) of 3 before transmission, and the value of n in the defer periodcan be 0, 1 or 2, depending on actual situations. When the number (A) ofsuccessive scheduled subframes falls into [m3, m4], the LAA UE can use aminimum CW larger than that used for [ml, m2] before transmission, andso on.

Embodiment 4

In this embodiment, the related indication information is one or morebits configured in DCI signaling. The LBT mechanism and/or LBT mechanismparameter set can be determined based on the related indicationinformation by: preconfiguring bit information and/or numbers of bitsconfigured in the DCI signaling corresponding to the respective LBTmechanisms and/or LBT mechanism parameter sets; and selecting the LBTmechanism and/or LBT mechanism parameter set corresponding to the bitinformation and/or the number of bits configured in the DCI signalingfor contention-based channel access.

Preferably, different bit information configured in the DCI signalingcan refer to values of a specified IE field, e.g., integer values from 0to N, corresponding to different LBT mechanisms and/or LBT mechanismparameter sets. Assuming that the IE field contains 3 bits, nine (0-8)LBT mechanisms and/or LBT mechanism parameter sets can be determined.For example, when the IE field has a value of 000, it indicates to theUE that the LBT Cat2 in which only one CCA is performed can be selected;when the IE field has a value of 001, it indicates to the UE that theLBT Cat2 mechanism in which more than one CCA is performed can beselected;

when the IE field has a value of 010, it indicates to the UE that theLBT Cat4 mechanism or the LBT Cat4 mechanism having the minimum CW canbe selected, and so on. As the value of the IE field increases, the CWsize increases successively. The LBT mechanism parameter set can includeother parameters such as a defer period n, a slot length of the firstCCA, and the like.

If the DCI signaling contains a random back-off value N in the intervalof [0, q-1] and a transmitting device can correctly decode the DCIsignaling, then the transmitting device can determine the LBT mechanismbefore transmission based on the random back-off value N. Here, q has avalue in the interval of [CWmin, CWmax] corresponding to the LBT Cat4mechanism. If the DCI signaling carries the random back-off value N butthe transmitting device fails to decode it, the transmitting devicecannot determine whether it did not obtain the random back-off value Nbecause it failed to decode the DCI signaling correctly or because theDCI signaling did not carry the value N at all. In this case, thetransmitting device can use a predetermined LBT mechanism forcontention-based channel access.

Embodiment 5

In this embodiment, the related indication information is a broadcastscheme. The LBT mechanism and/or LBT mechanism parameter set can bedetermined based on the related indication information by: selecting theLBT mechanism and/or LBT mechanism parameter set based on an identity ofan LBT mechanism or a category of an LBT mechanism parameter setbroadcasted to a transmitting device.

In particular, the broadcast scheme means that the LBT mechanism and/orLBT mechanism parameter set to be selected for contention-based channelaccess can be broadcasted directly to the transmitting device. Forexample, a base station can broadcast to the transmitted device a randomback-off value N=0 in an LBT mechanism parameter set. The transmittingdevice can know from the parameter that it needs to apply the LBT Cat2without random back-off before a scheduled subframe. Alternatively, theenhanced LBT Cat2 mechanism can be used. In this embodiment, a slotlength of CCA can be predefined or configured by the base station, orcan be a default value. Similarly, when a random back-off value N=3 isbroadcasted, the contention-based channel access can be performed inaccordance with the LBT Cat4 mechanism with the random back-off valueN=3 in an ECCA process.

Embodiment 6

In this embodiment, the related indication information is a time-domainlength of a gap between an uplink burst and a downlink burst. Thetime-domain length of the gap between the uplink burst and the downlinkburst can be signaled from a base station, determined based on therespective lengths of the uplink burst and the downlink burst (which isa common practice in the art), or preconfigured (e.g., based mainly onan empirical value).

In particular, when the time-domain length of the gap between the uplinkburst and the downlink burst is smaller than 16 μs or 25 μs, no LBTmechanism may be applied before transmission of the uplink transmissionburst. When the time-domain length of the gap between the uplink burstand the downlink burst is one OFDM symbol and the start position ofcontention-based channel access using a selected LBT mechanism is in thesecond half of one OFDM symbol, the LBT Cat2 mechanism can be usedbefore data transmission. Alternatively, when only the LBT Cat4mechanism can be used in the uplink, the transmitting device can use theLBT Cat4 having the minimum CW value before transmission. When thetime-domain length of the gap between the uplink burst and the downlinkburst is one OFDM symbol and the LBT starts in the middle interval ofone symbol, the transmitting device can use the LBT Cat2 mechanism inwhich more than one CCA is performed before transmission. Here, whenthere are two LBT modes, e.g., LBT Cat2 mechanism and LBT Cat4mechanism, in the uplink, the LBT Cat2 or enhanced LBT Cat2 can be usedin the first uplink subframe in the uplink transmission burst, while theLBT Cat2 is used, or no LBT mechanism can be performed, in subsequentsubframes, so as to improve the probability of uplink channel access andthe uplink resource efficiency. Alternatively, when there is only oneLBT Cat4 mechanism in the uplink, the LBT

Cat4 having as small CW as possible can be used in the first uplinksubframe in the uplink transmission burst. Optionally, the same LBT Cat4parameter configuration as the first subframe, or the LBT Cat4mechanisms having successively decreasing CWs, can be used in thesubsequent uplink subframes. This is also the case when the time-domainlength of the gap between the uplink burst and the downlink burst is oneOFDM symbol and the LBT starts in the first half of one symbol.Similarly, the above scheme also applies when the time-domain length ofthe gap between the uplink burst and the downlink burst is longer thanone OFDM symbol, e.g., the LBT Cat2 or the LBT Cat4 having as small CWas possible (e.g., having CWmin=1, CWmax=3 and n=1 in the defer period)can be used in the first uplink subframe.

In another case, the LBT mechanism and/or LBT mechanism parameter set tobe used before transmission can be indicated directly by the time-domainlength of the gap between the uplink burst and the downlink burst. Forexample, when the time-domain length of the gap is smaller than apredetermined threshold, which can be 16 μs or 25 μs, no LBT mechanismmay be applied before transmission of the uplink transmission burst, andno LBT mechanism may be applied in other uplink subframes in the burst.Optionally, in order to avoid the hidden station problem, an LBT Cat2process can be performed. When the time-domain length of the gap islarger than 16 μs or 25 μs, preferably the LBT Cat2 mechanism can beused for contention-based channel access. If there is only one LBTmechanism, e.g., LBT Cat4, in the uplink, the LBT Cat4 process having assmall CW as possible can be used due to the short time-domain length ofthe gap. For each subsequent subframe, an LBT process having a smallerCW than its previous subframe can be used. For example, the LBT Cat2 canbe used, or no LBT can be applied, in the last uplink subframe in theburst. Optionally, in the subsequent subframes, the same LBT mechanismor LBT mechanism parameter set as the first subframe can be used forcontention-based channel access. Alternatively, no LBT mechanism or LBTmechanism parameter set can be applied.

FIG. 3 is a schematic diagram showing a position of an area in which anLBT mechanism and/or an LBT mechanism parameter set is applied accordingto Embodiment 6 of the present disclosure. As shown in FIG. 3,contention-based channel access can be performed using an LBT mechanismand/or LBT mechanism parameter set selected corresponding to thetime-domain position or time length of the gap between the uplink burstand the downlink burst.

Embodiment 7

The switching related information is an identity in an LBT list signaledfrom a base station. The LBT mechanism and/or LBT mechanism parameterset can be determined based on the related indication information by:preconfiguring an information list of LBT mechanisms for switching, tobe shared between that transmitting device and a base station; anddetermining, by a transmitting device, the LBT mechanism and/or LBTmechanism parameter set based on list information signaled from the basestation.

Table 1 is the list information shared between the base station and thetransmitting device according to Embodiment 7 of the present disclosure.The LBT mechanisms for contention-based channel access included in thelist are shown in Table 1.

TABLE 1 Index Candidate LBT mechanism for uplink 1 LBT Cat2 mechanism inwhich only one CCA is performed 2 LBT Cat2 mechanism in which more thanone CCA is performed 3 LBT Cat4 having a CW interval of [P1, P2] 4 LBTCat4 having a CW interval of [S1, S2] 5 LBT Cat4 having a CW interval of[K1, K2] . . . LBT Cat4 having a CW interval of . . .

Here, the start position of CCA in the LBT Cat2 can be a fixed positionor a start position randomly selected in time-domain available for LBT.

When the LBT mechanism for contention-based channel access is an LBTCat4 mechanism, the list information shared between the base station andthe transmitting device includes various LBT mechanism parameter setsfor the LBT Cat4 mechanism as determined based on CW sizes, as shown inTable 2.

TABLE 2 Index Candidate LBT mechanism for uplink 1 LBT Cat4 having a CWinterval of [P1, P2] 2 LBT Cat4 having a CW interval of [S1, S2] 3 LBTCat4 having a CW interval of [K1, K2] . . . LBT Cat4 having a CW valueof . . .

In Table 1 and Table 2, the values of CW sizes may successively increaseand the value of n in the defer period in the LBT Cat4 mechanismparameter set can preferably be 1.

Alternatively, the value of n can be 0 or 2. Further, the values of n inthe LBT Cat4 candidates in the list may be the same or different.Optionally, for the first uplink subframe, channel access can beperformed as scheduled or as indicated by the base station. Preferably,for cross-carrier scheduling, when there is no data to be transmitted indownlink, a UE can obtain using a mechanism or determine autonomously aparameter having a large CW value in the selectable information list forcontention-based channel access. For the subsequent uplink subframes,the contention-based LBT mechanisms having successively decreasing CWvalues, or more simplified LBT mechanisms, can be used. Alternatively,for the subsequent uplink subframes, the same LBT mechanism or LBTmechanism parameter set as the first uplink subframe can be used forcontention-based channel access, or no LBT mechanism or LBT mechanismparameter set will be applied.

When there are only LBT mechanisms for contention-based access in theLBT information list, after the UE has obtained the LBT mechanism to beused, it can perform the contention-based channel access further basedon an LBT parameter configuration corresponding to a traffic type ofdata to be transmitted or a priority of a transmitted channel or signal.Alternatively, it can further determine the specific LBT parameter setin the LBT mechanism based on the length of the transmission burst, theindex of the uplink subframe in the burst, a retransmission or aninitial transmission, so as to perform the channel access.

Optionally, if the UE has failed for a number of times in channel accessin accordance with the LBT mechanism or LBT mechanism parameter set, itcan improve or use a more simplified LBT mechanism or an LBT Cat4 havinga smaller CW or raise the priority (thereby using an LBT mechanism orLBT mechanism parameter configuration corresponding to the higherpriority), autonomously or in accordance with Channel State Information(CSI) within a predetermined time length, a Reference Signal ReceivedPower (RSRP) within a predetermined time length, a Reference SignalReceived Quality (RSRQ) within a predetermined time length, HybridAutomatic Repeat reQuest - Acknowledge (HARQ-ACK) information, orinformation on a measured interference.

Similarly, if the UE has succeeded for a number of times in channelaccess in accordance with the LBT mechanism or LBT mechanism parameterset, in order to provide fair opportunities for contention-based access,the principle for handling contention-based channel access failures canalso be applied to adjust the determined LBT mechanism or LBT mechanismparameter set.

With the above information list, the transmitting device can performcontention-based channel access using an LBT mechanism having an indexin the information list as indicated by the base station to thetransmitting device or an LBT mechanism selected autonomously by thetransmitting device from the information list.

Embodiment 8

In this embodiment, the related indication information is a position ofa scheduled subframe in a transmission burst or in uplink subframes, theLBT mechanism and/or LBT mechanism parameter set can be determined basedon the related indication information by: preconfiguring positions ofthe scheduled subframe in the transmission burst or positions of thescheduled subframe in the uplink subframes corresponding to respectiveLBT mechanisms and/or LBT mechanism parameter sets; and determining theLBT mechanism and/or LBT mechanism parameter set based on the positionof the scheduled subframe in the transmission burst or in the successiveuplink subframes.

Preferably, respective LBT Cat4 mechanism parameter configurations canbe selected in a descending order of CW size based on the position ofthe subframe in which the UE is scheduled in the uplink subframes in onetransmission burst or in the uplink subframes. Optionally, an LBTmechanism without random back-off, or no LBT mechanism, can be appliedin uplink subframes subsequent to the first uplink subframe. If thecontention-based access in accordance with the LBT mechanism and/or LBTmechanism parameter set selected based on the position of the firstuplink subframe has failed, in the next uplink subframe, the LBTmechanism and/or LBT mechanism parameter set corresponding to thesubframe where the failure occurs can be used again, or a moresimplified LBT mechanism or an LBT parameter configuration having asmaller CW can be used.

For example, for the first scheduled uplink subframe, CWmax=7, CWmin=5,and n=1. If the first subframe fails, the same configuration can stillbe used for the second scheduled uplink subframe. Alternatively, for thesecond scheduled uplink subframe, CWmax=4, CWmin=2, and n=1; CWmax=3CWmin=1, and n=1; CWmax=1, CWmin=1, and n=1; and so on.

This embodiment will be explained with reference to an example where thetransmitting device can only use the LBT Cat4 as its LBT mechanism forcontention-based access in uplink. Optionally, when the random back-offvalue N is 0, the contention-based access mechanism is degraded into theLBT Cat2.

When a special subframe precedes the uplink subframe, preferably the LBTmechanism for contention-based access is the normal LBT Cat4 mechanism.The normal LBT Cat4 mechanism is a process of a first CCA plus a deferperiod plus an ECCA process having a random back-off process N. Thenormal LBT Cat4 mechanism has a maximum CW value smaller than the CW ofthe downlink LBT mechanism. The maximum CW can be 1024 at maximum and 1at minimum. For example, the minimum CW can be 15, the maximum CW can be31 or 63, and the component n in the defer period can have a maximumconfigurable range of [0, 2]. Preferably, the value of n can be 1, inorder to avoid interference with neighboring nodes as much as possible,reduce the collision probability and increase the success rate ofchannel access by the device.

For a downlink subframe or a time-domain length of a gap precedes thefirst uplink subframe in the transmission burst or the first scheduleduplink subframe, preferably the LBT mechanism for contention-basedaccess is the normal LBT Cat4 mechanism. It is to be noted here that themaximum CW of the LBT mechanism is in a smaller CW range than that forthe special subframe. For example, the minimum CW (CWmin) can be 7, themaximum CW (CWmax) can be 15, and the component n in the defer periodcan have a maximum configurable range of [0, 2]. Preferably, the valueof n can be 1.

For the second uplink subframe in the transmission burst or the seconduplink subframe in which the UE is successively scheduled, preferablythe LBT mode is selected as the LBT Cat4 mechanism having a CW smalleronly than the maximum CW value. For example, the minimum CW (CWmin) canbe 3, the maximum CW (CWmax) can be 7, and the component n in the deferperiod can have a maximum configurable range of [0, 2]. Preferably, thevalue of n can be 1.

Similarly, for the third uplink subframe in the transmission burst orthe third uplink subframe in which the UE is successively scheduled,preferably the LBT mechanism is selected as the LBT Cat4 mechanismhaving a CW smaller only than the CW values for the first and seconduplink subframes. For example, the minimum CW (CWmin) can be 1, themaximum CW (CWmax) can be 3, and the component n in the defer period canhave a maximum configurable range of [0, 2]. Preferably, the value of ncan be 1.

For the fourth uplink subframe in the transmission burst or the fourthuplink subframe in which the UE is successively scheduled, preferablythe LBT mechanisms is selected as the LBT Cat4 mechanism having a CWsmaller only than the CW values for the first, second and third uplinksubframes, the LBT Cat3 having a fixed CW (i.e., CWmax=CWmin), or theLBT Cat2 having a random back-off value N=0. For example, the minimum CW(CWmin) can be 1, the maximum CW (CWmax) can be 1, and the value of Nmay be in the interval of [0, q-1], where q can have a maximum value of1 (i.e., the random back-off value N can only be 0). The component n inthe defer period can have a maximum configurable range of [0, 2].Preferably, the value of n can be 1. Alternatively, the minimum CW andthe maximum CW can each be 2. Similarly, LBT Cat2 detection slots havingdifferent time lengths can be further used, or the enhanced LBT Cat2 canbe used. In the above cases, the values of the component n in the deferperiod can be the same or can be configured differently in differentsituations.

When the same or different UEs are successively scheduled in a number ofsubframes, the normal LBT Cat4 can be used for the first uplink subframeand no LBT may be applied for the subsequent subframes. Alternatively,the normal LBT Cat4 can be used for the first uplink subframe and theLBT Cat4 mechanisms having successively decreasing CW sizes can beapplied for the subsequent subframes for contention-based channelaccess. Alternatively, the normal LBT Cat4 can be used for the firstuplink subframe and the LBT Cat2 or a fast LBT mechanism can be used forthe subsequent subframes. Alternatively, the LBT Cat2 mechanism can beused for the first uplink subframe and no LBT mechanism may be appliedfor the subsequent subframes. Alternatively, the LBT Cat2 mechanism canbe used for the first uplink subframe and the LBT Cat2 mechanism and/orno LBT mechanism may be applied for the subsequent subframes.Alternatively, the above described scheme can be used.

Embodiment 9

In this embodiment, one or more random back-off values can beconfigured. It can be determined to use the configured random back-offvalue via same-carrier scheduling or cross-carrier scheduling based on aposition of a scheduled uplink subframe or a length of a transmissionburst, or based on whether a Pcell has received grant information.

A base station can configure a transmitting device with the same timelength of CCA and different UEs can be configured with different CCApositions. In the former case, different UEs can be configured withdifferent CCA positions for mitigating unfairness in contention-basedaccess, thereby further improving the overall uplink system performance.For a transmitting device that first detects a channel to be idle, if astart boundary of a data transmission has not arrived at the time whenthe channel is successfully detected to be idle, it can transmit areservation signal or an initial signal for identification by UEs to bemultiplexed in the same cell, so as to achieve the multiplexing. In thelatter case, when a UE detects a channel to be busy during randomback-off, it can reconfigure the random back-off value in the nextchannel detection or when a particular threshold is exceeded. In thiscase, the reconfigured random back-off value N is smaller than thecurrent value of N. With the method in this embodiment, the base stationcan accelerate the decreasing of the random back-off value N, so as toallow fast channel access by an LAA device, thereby improving thechannel access rate. If a device has successively detected the channelto be busy for more than a predetermined threshold time length during atime period, the N value can be adjusted again. If a device hassuccessively detected the channel to be busy more than a predeterminedthreshold number of times, the N value can be adjusted too. Thepredetermined thresholds can be determined empirically by those skilledin the art.

Embodiment 10

In this embodiment, the related indication information is a carrierscenario for transmission of a scheduling instruction. The LBT mechanismand/or LBT mechanism parameter set can be determined based on therelated indication information by: determining the LBT mechanism and/orLBT mechanism parameter set based on same-carrier scheduling orcross-carrier scheduling.

Preferably, for the uplink, the existing scheduling mechanisms includesame-carrier scheduling and cross-carrier scheduling. Here, differentLBT mechanisms or different types of CW values in a specific LBTmechanism can be selected for the same-carrier scheduling and thecross-carrier scheduling. Of course, the same mechanism or the same CWparameter configuration can be selected. When different mechanisms areselected, for the same-carrier scheduling, a base station has appliedthe downlink LBT Cat4 mechanism once before transmitting schedulinggrant information. Hence, when a transmitting device receives the grantinformation, it can select to apply a fast LBT mechanism beforetransmission of the first uplink subframe. Since a Wi-Fi system performsonly one LBT process before data transmission and in an LAA system abase station in the same-carrier scheduling mode has applied an LBTmechanism similar to the Wi-Fi system once, when the UE receives thegrant information, it can apply one fast LBT mechanism beforetransmission. This is advantageous in avoiding the hidden node problem.Optionally, when a time-domain length of a gap before an uplink ordownlink transmission is smaller than a predetermined threshold, whichcan be 16 μs or 25 μs, a UE can select to apply no LBT mechanism or LBTmechanism parameter set. Here, the fast LBT mechanism can include thenormal LBT Cat4 mechanism having its maximum CW smaller than the CW forthe downlink LBT Cat4; the defer period+ECCA process; the direct ECCAprocess; the enhanced LBT Cat2; and the LBT Cat2. A fast LBT mechanism(which can be the same as or different from the fast LBT mechanism usedfor the first uplink subframe) can be used for the subsequent uplinksubframes. For example, the defer period+ECCA process (CWmax=7, CWmin=5and n=1) can be used for the first uplink subframe. The same deferperiod+ECCA process, or different fast LBT mechanisms, or the same fastLBT mechanism having different CW sizes or different time lengths ofCCA, can be used for the subsequent, successive uplink subframes. Forexample, the direct ECCA process (CWmax=6, CWmin=4 and n=1) can be usedfor the second subframe. The enhanced LBT Cat2, LBT Cat2 or no LBTmechanism can be applied for the third subframe. Alternatively, the fastLBT mechanism can be applied only for the first uplink subframe, whileno LBT mechanism is applied for the subsequent, successive uplinksubframes.

For the cross-carrier scheduling, there are different cases where thereis downlink data to be transmitted and where there is no downlink datato be transmitted.

When there is downlink data to be transmitted and uplink grantinformation is transmitted over a licensed carrier, the LBT mechanismapplied in the first uplink subframe can be the same as that in the caseof same-carrier scheduling.

When there is no downlink data to be transmitted and the uplink grantinformation is transmitted over a licensed carrier, as the base stationtransmits the uplink grant information over the licensed carrier, no LBTmechanism or LBT mechanism parameter set needs to be applied. Hence,after receiving the grant information, the UE needs to apply the normalLBT Cat4 mechanism before data transmission, so as to achieve a faircontention-based channel access with a Wi-Fi system. However, themaximum CW for the normal LBT Cat4 should be smaller than the CW for thedownlink LBT Cat4. For subsequent uplink subframes, no LBT mechanism maybe applied for transmission. Alternatively, the LBT Cat4 mechanismhaving a smaller CW than the previous subframe can be appliedsequentially. When the LBT Cat4 and the LBT Cat2 are used in the uplink,for each of the subsequent uplink subframes, the LBT Cat4 process havinga smaller CW than its previous subframe and/or an LBT Cat2 process canbe performed. Alternatively, the LBT Cat2 can be applied for each of thesubsequent uplink subframes. Alternatively, the successively decreasingCWs, the LBT Cat2 and/or no LBT can be applied. Alternatively, for eachof the subsequent uplink subframes, the same LBT Cat4 can be applied andonly the random back-off value N over available resources can be used.

Optionally, in this embodiment, after the LBT mechanism has beenselected, different LBT parameter set configurations, including CWmax,CWmin, the component n in the defer period and the like, can be selectedmore specifically, depending on different QoS priority levels, differentchannel/signal priorities, or traffic information.

Embodiment 11

In this embodiment, the related indication information includes: a sizeof data packet to be transmitted, a number of successive scheduledsubframes, one or more bits configured in DCI signaling, a broadcastscheme, a time-domain length of a gap between an uplink transmissionburst and a downlink transmission burst, an identity in an LBT listsignaled from a base station, a position of a scheduled subframe in atransmission burst or in uplink subframes, a length of one transmissionburst, and/or a carrier scenario for transmission of a schedulinginstruction. An LBT mechanism and/or an LBT mechanism parameter set isdetermined based on related indication information. Contention-basedchannel access is performed based on the selected LBT mechanism and/orLBT mechanism parameter set. When there are a number of LBT mechanismsin the uplink, the LBT mechanism for the contention-based channel accesscan be determined as described above. When there is only one LBTmechanism in the uplink, in this embodiment, the LBT mechanism parameterset for the contention-based channel access can also be determined asdescribed above.

In this embodiment, priority information can include QoS priorities fordifferent traffic types or priorities of different channels and/orsignals and/or logical channels. Optionally, logical channels havingdifferent priority levels can be mapped to corresponding physicaltransmission channels, such that the physical transmission channels alsohave the respective priority levels. Here, among the logical channels inthe uplink, Common Control Channel (CCCH), Dedicated Control Channel(DCCH) and Dedicated Traffic Channel (DTCH) are mapped to an uplinktransmission channel known as Uplink Shared Channel (UL-SCH).Optionally, the priorities of the logical channels are, in descendingorder, as follows: Cell-Radio Network Temporary Identity (C-RNTI) fromUL-CCCH or data to be transmitted (the highest priority); Buffer StatusReport (BSR) and Medium Access Control (MAC) Control Element (CE) forBSR without padding; MAC CE for transmission Power Headroom (PHR) orextended PHR; data in any logical channel, except those for Uplink ChinaCompulsory Certification (UL-CCC); and BSR with padding (the lowestpriority).

When the LBT mechanism and/or LBT mechanism parameter set is determinedbased on the priority information, if there are a number of LBTmechanisms in the uplink, the LBT mechanism and/or LBT mechanismparameter set can be selected based on different priority information.When there is only one LBT mechanism in the uplink, the parameter set inthe LBT mechanism can be selected based on different priority levels.Then, the contention-based channel access can be performed based on theLBT mechanism and/or LBT mechanism parameter set corresponding to thepriority.

Here, it is assumed that a UE is to transmit only data of one traffictype, but has failed for a number of times successively in channelaccess in accordance with the selected LBT mechanism or LBT parameterset (e.g., perhaps the corresponding priority is low and thus a large CWvalue or a long CCA time length is used in the LBT mechanism). In thiscase, the following schemes can be applied according to this embodiment.

Scheme 1: The transmitting device senses and reports information on ameasured interference or Channel State Information (CSI) to the basestation, which decides to adjust the priority level of the LBT mechanismor LBT mechanism parameter set used for the UE to transmit the data ofthat traffic type. For example, if the LBT Cat4 mechanism having thelargest CW was used in the failed contention-based access, the CW sizecan be reduced or the priority level can be raised by a certain level(which can be 1 by default) and thus the LBT mechanism or LBT mechanismparameter set can be adjusted. When there is only one LBT mechanism inthe uplink, e.g., LBT Cat4, if the UE always uses the LBT Cat4 (CWmin=7,CWmax=15, and n=1 in the defer period) to transmit that type of traffic(assuming a priority of 3), it can use a smaller CW size or a higherpriority in the next LBT (e.g., LBT Cat4 having CWmin=5, CWmax=7, andn=1 in the defer period) or the LBT mechanism parameter setcorresponding to the higher priority, based on the measurementinformation. When there is a plurality of LBT mechanisms in the uplink,preferably a small CW value in a corresponding LBT mechanism or an LBTparameter set corresponding to a priority one or more levels higher canbe used for contention-based channel access. In a suboptimal scheme, amore simplified fast-access LBT mechanism, such as the enhanced LBT Cat2or the LBT Cat2, can be used. As a general principle, the priority levelor the used LBT mechanism or LBT parameter set configuration can befurther adjusted based on the reported measured interference or feedbackinformation.

Scheme 2: When the contention-based access based on the LBT mechanismand/or LBT mechanism parameter set has failed for a first predeterminedthreshold number of times, the

UE can raise the priority level according to a predefined rule. Forexample, a priority offset can be 1 and the first predeterminedthreshold number can be 5. If the UE has failed successively for 5 timesin performing the LBT in accordance with the LBT mechanism or LBTparameter set corresponding to the priority 3, the priority can beraised by one priority level according to the predefined priorityoffset. That is, the LBT mechanism or LBT parameter set corresponding tothe priority 2 will be used for the next contention-based channelaccess. Similarly, when the LBT has succeeded successively for a numberof times, the above process for successive failures can also be used,except that the priority is lowered or the CW value is increased. Indoing so, it is possible to reduce the probability of channel access, soas to give more opportunities for other devices to access the channel,thereby ensuring the fairness.

In this embodiment, the above process can also be applied at the basestation. In Scheme 1, the base station can sense a measurement totrigger the adjustment of the LBT mechanism or LBT parameter set. Themeasurement may include: Channel State Information (CSI) within apredetermined time length, a Reference Signal Received Power (RSRP)within a predetermined time length, a Reference Signal Received Quality(RSRQ) within a predetermined time length, Hybrid Automatic RepeatreQuest - Acknowledge (HARQ-ACK) information, or information on ameasured interference.

For an initial transmission and a retransmission, different LBTmechanisms can be applied (when there is a plurality of LBT mechanismsin the uplink), or an LBT mechanism parameter set can be selectedaccordingly (when there is only one LBT mechanism in the uplink). Whenthe contention-based access based on the LBT mechanism and/or LBTmechanism parameter set has failed for the first predetermined thresholdnumber of times, the LBT mechanism and/or LBT mechanism parameter set tobe used for contention-based access in the retransmission can beadjusted using Scheme 1 or Scheme 2.

Embodiment 12

In this embodiment, a process to be performed when a plurality ofdifferent priority levels in a transmission burst, i.e., when priorityinformation includes a plurality of priority levels, will be mainlydescribed.

It is assumed that there are three transmitting devices scheduled in onetransmission burst, corresponding to priority levels of 1 (the highestpriority), 2 and 3 (the lowest priority), respectively. In turn, thepriority levels of 1, 2 and 3 correspond to the following LBT parametersets, respectively: LBT Cat4 having CWmin=1 and CWmax=3; LBT Cat4 havingCWmin=4 and CWmax=5; and LBT Cat4 having CWmin=5 and CWmax=7. When thereis a plurality of priorities in one transmission burst, an LBT mechanismand/or an LBT mechanism parameter set can be determined in accordancewith a predetermined priority policy. There can be the followingschemes.

Scheme 1: Each transmitting device performs contention-based channelaccess based on an LBT mechanism parameter set corresponding to thelowest priority. Here, it is assumed that UE1 corresponds to thepriority 1 and UE2 corresponds to the priority 2. In this case, both UE1and UE2 need to perform contention-based channel access based on an LBTmechanism parameter set for the priority 3 corresponding to UE3. In thisway, UE1, which has the highest priority and would otherwise be likelyto succeed in LBT and access an unlicensed carrier, performs LBT usingthe LBT parameter corresponding to the lowest priority and thus has avery high probability to fail in the contention. Hence, none of thethree UEs may access the unlicensed carrier.

Scheme 2: Each transmitting device performs contention-based channelaccess based on an LBT mechanism parameter set corresponding to thesecond highest priority. In this way, it is possible to ensure that atleast one UE can successfully access the unlicensed carrier.

Scheme 3: Each transmitting device performs contention-based channelaccess based on an LBT mechanism parameter set corresponding to thehighest priority. In this way, it is possible to ensure that theplurality of UEs, or a plurality of traffic types and/orchannels/signals, in the burst can access the unlicensed carrier,thereby allowing normal transmissions.

Scheme 4: The LBT mechanism parameter set corresponding to the highestpriority is used, with q having a value of CWmin.

Scheme 5: Each transmitting device performs contention-based channelaccess based on a predetermined LBT mechanism or LBT parameter setcorresponding to its priority.

Optionally, this can be done in parallel in the time domain and by meansof frequency division multiplexing in the frequency domain.Alternatively, this can be done in parallel in the time domain andacross an entire bandwidth in the frequency domain.

Scheme 6: The transmitting devices perform contention-based channelaccess in a time division manner. Here, they may have common start timefor performing LBT. When a channel is detected to be busy, their randomback-off values N are frozen.

Embodiment 13

In this embodiment, a process to be performed when an LBT process is tobe applied in a case where a transmitting device (or UE) is scheduled ondifferent subframes and Resource Elements (REs) or Resources Blocks(RBs) at positions are scheduled on the different subframes will bedescribed.

In particular, in this embodiment, it is assumed that the UE isscheduled in different RBs or REs in Subframe 1 and Subframe 2,respectively. In this case, an LBT mechanism or an LBT parameter set canbe applied in accordance with one of the following schemes.

Scheme 1: The UE performs an LBT process on one or more OFDM symbolsbefore Subframe 1 and over the entire bandwidth in the frequency domain.Before Subframe 2, a full-bandwidth LBT process can be performed.Alternatively, an LBT process can be performed over frequency-domainresources corresponding to scheduled resources in the second scheduledsubframe, or no LBT process may be performed.

Scheme 2: The UE performs an LBT process on one or more OFDM symbolsbefore Subframe 1 and over respective scheduled resources in thefrequency domain. An LBT process can be performed before Subframe 2 andat frequency-domain positions of scheduled resources corresponding toSubframe 2, or no LBT process may be performed.

Scheme 3: The UE performs an LBT process on one or more OFDM symbolsbefore Subframe 1 and at frequency-domain positions of scheduledresources corresponding to Subframe 1. An LBT process can be performedon the last one or more symbols in Subframe 1 and at frequency-domainpositions of scheduled resources corresponding to Subframe 2.

When the UE is scheduled in the same RB or RE positions in Subframe 1and Subframe 2, respectively, an LBT process can be performed inaccordance with one of the following schemes.

Scheme 1: The UE performs an LBT process on one or more OFDM symbolsbefore

Subframe 1 and over the entire bandwidth in the frequency domain. BeforeSubframe 2, a full-bandwidth LBT process can be performed, or no LBTprocess may be performed.

Scheme 2: The UE performs an LBT process on one or more OFDM symbolsbefore Subframe 1 and at frequency-domain positions of scheduledresources. Similarly, in the second subframe, an LBT process can beperformed at frequency-domain positions of scheduled resources, or noLBT process may be performed.

When the UE is scheduled in the alternate RB or RE positions in Subframe1 and Subframe 2, respectively, an LBT process can be performed inaccordance with one of the following schemes.

Scheme 1: The UE performs an LBT process on one or more OFDM symbolsbefore Subframe 1 and over the entire bandwidth in the frequency domain.Before Subframe 2, a full-bandwidth LBT process can be performed.Alternatively, an LBT process can be performed over frequency-domainresources corresponding to scheduled resources in the second scheduledsubframe, or no LBT process may be performed.

Scheme 2: The UE performs an LBT process on one or more OFDM symbolsbefore Subframe 1 and over a union of frequency-domain resourcescorresponding to two scheduled resources (e.g., for UE1 , when thescheduled frequency-domain subframes in Subframe 1 are PRB#2-PRB#5 andthe scheduled frequency-domain subframes in Subframe 2 are PRB#4-PRB#7,the frequency-domain positions at which the LBT process is performedbefore the first subframe are PRB#2-PRB#7). An LBT process can beperformed before Subframe 2 and over frequency-domain resourcescorresponding to scheduled resources of the second scheduled subframe orover a union of the corresponding scheduled resources, or no LBT processmay be performed.

Scheme 3: The UE performs an LBT process on one or more OFDM symbolsbefore Subframe 1 and over respective scheduled resources in thefrequency domain. An LBT process can be performed before Subframe 2 andat frequency-domain positions of scheduled resources corresponding toSubframe 2, or no LBT process may be performed.

Scheme 4: The UE performs an LBT process on one or more OFDM symbolsbefore Subframe 1 and at frequency-domain positions of scheduledresources corresponding to Subframe 1. An LBT process can be performedon the last one or more symbols in Subframe 1 and at frequency-domainpositions of scheduled resources corresponding to Subframe 2.

The above schemes also apply when different UEs are scheduled at thesame, different or alternate resource positions in different subframes.

Further, regarding the LBT mechanism or LBT parameter set to be usedwhen the same UE or different UEs are scheduled on a plurality ofsuccessive uplink subframes, reference can be made to the aboveEmbodiment 10, where the LBT process is performed on different subframesin accordance with different scheduling schemes and situations of theplurality of successive subframes. Alternatively, the normal LBT Cat4can be applied for the first uplink subframe and no LBT can be appliedon the subsequent subframes. Alternatively, the normal LBT Cat4 can beapplied for the first uplink subframe and contention-based access can beperformed on the subsequent subframes with successively decreasing CWs.Alternatively, the normal LBT Cat4 can be applied for the first uplinksubframe and the LBT Cat2 or the fast LBT mechanism can be applied onthe subsequent subframes. Alternatively, the LBT Cat2 mechanism can beapplied for the first uplink subframe and no LBT mechanism can beapplied on the subsequent uplink subframes. Alternatively, the LBT Cat2mechanism can be applied for the first uplink subframe and the LBT Cat2mechanism, or no LBT mechanism, can be applied for the subsequent uplinksubframes.

Embodiment 14

In this embodiment, a process will be described, in which respectivedifferent LBT mechanisms or LBT parameter sets are used forcontention-based channel access before transmission for a plurality ofsuccessive uplink subframes in one uplink transmission burst.

In this embodiment, when all subframes are uplink subframes, the firstuplink subframe is used as a position for applying the LBT mechanism orLBT mechanism parameter set before the second uplink subframe. For eachof subsequent successive uplink subframes, the last OFDM symbol of theprevious uplink subframe is used as a position for applying the LBTmechanism or LBT mechanism parameter set for that uplink subframe.

For a TDD frame structure, the subframe before a plurality of successiveuplink subframes is a special subframe, S. In this case, the positionfor applying the LBT mechanism or LBT mechanism parameter set beforetransmission of the first uplink subframe can be the GP or UpPTS in thespecial subframe. For each of subsequent successive uplink subframes,the last OFDM symbol of the previous uplink subframe can be used as theposition for performing LBT for that uplink subframe.

Here, the LBT process for the first uplink subframe may occupy aplurality of OFDM symbols, and the LBT process for each of thesubsequent uplink subframes may occupy one or two OFDM symbols of itsprevious subframe. The same also applies to a structure having aflexible uplink-downlink frame ratio.

In the following, the LBT mechanisms or LBT mechanism parameter sets tobe applied for transmission on a plurality of successive uplinksubframes in accordance with different scheduling mechanisms will beexplained in association with the scheduling mechanisms and differentpositions of uplink subframes.

For the same-carrier scheduling, a base station has applied the downlinkLBT Cat4 mechanism before transmitting uplink scheduling grantinformation over an unlicensed carrier. Hence, when receiving the grantindication information, the UE can operate as follows beforetransmission of the first uplink subframe.

Scheme 1: When a slot length of a gap between an uplink transmissionburst and a downlink transmission burst is a predetermined threshold,which can be 16 μs or 25 μs, the scheduled UE may apply no LBT mechanismbefore transmission of the first uplink subframe. However, this may leadto the hidden node problem.

Scheme 2: The scheduled UE may apply a fast LBT mechanism beforetransmission of the first uplink subframe. Here, the fast LBT mechanismcan include the defer period +ECCA process; the direct ECCA process; theenhanced LBT Cat2; the LBT Cat2 and the simplified LBT Cat4 (having a CWsmaller than the CW for the downlink LBT Cat4 and n in the defer periodbeing configurable in [0, 2]). In this case, the fast LBT mechanismapplied for the first uplink transmission can be one of the above fastLBT mechanisms.

Optionally, before transmission of each of a plurality of subsequentsuccessive uplink subframes, a fast LBT mechanism can be applied on thelast OFDM symbol of its previous subframe. Here, the fast LBT mechanismfor the first uplink subframe and the fast LBT mechanism for theplurality of subsequent successive uplink subframes may be the same ordifferent. Optionally, more simplified fast LBT mechanisms can beapplied in turn (e.g., the defer period+ECCA process having CWmax=4 canbe applied for the first uplink subframe; the direct ECCA process havinge.g., CWmax<4 can be applied for the second uplink subframe; and theenhanced LBT Cat2 can be applied for the third uplink subframe).Optionally, a fast LBT mechanism can be applied for the first uplinksubframe and the same LBT mechanism can be applied for each of theplurality of subsequent successive uplink subframes. In a special case,a fast LBT mechanism can be applied for the first uplink subframe and noLBT mechanism can be applied for the plurality of subsequent successiveuplink subframes. The above process for the same-carrier scheduling isprovided to share a fair opportunity of contention-based channel accesswith a Wi-Fi system. A node in the Wi-Fi system only needs to apply amechanism similar to the downlink LBT Cat4 mechanism once before datatransmission, with CWmax=1024. Hence, for the same-carrier scheduling,since the base station has applied the downlink LBT Cat4 mechanism oncebefore transmitting the uplink grant information, in order not to putthe LAA system in a disadvantageous position for contention-basedaccess, the UE only applies one fast LBT mechanism before uplinktransmission, so as to allow the UE to access the channel at a higherprobability or access the channel fast for transmission.

For the cross-carrier scheduling, two aspects will be describedregarding different LBT mechanisms or LBT parameter sets to be appliedfor different uplink subframes when a plurality of uplink subframes isto be transmitted.

When the uplink grant information is transmitted over a licensed carrierand no downlink data is to be transmitted, after receiving the uplinkgrant information, the UE can apply a normal LBT Cat4 mechanism on aplurality of OFDM symbols before the first uplink subframe, so as toensure a relatively fair opportunity for the Wi-Fi system to access thechannel. Here, the normal LBT Cat4 mechanism has a CW larger than the CWfor the downlink LBT Cat4 mechanism and optionally larger than the CWfor the same-carrier mechanism. The position of applying LBT for each ofthe plurality of subsequent successive uplink subframes is at the lastOFDM symbol of the previous subframe, with LBT Cat4 mechanisms havingsuccessively decreasing CW sizes (the CW sizes are selected such thatthe LBT processes can be finished within one OFDM symbol). Optionally, afast LBT mechanism can be applied for the transmission on the subsequentuplink subframes. Further, for the subsequent uplink subframes, the sameor different LBT mechanisms or LBT parameter sets can be used.Optionally, for a plurality of successive uplink subframes subsequent tothe first uplink subframe in one transmission burst, no LBT can beapplied for transmission.

When the uplink grant information is transmitted over a licensed carrierand there is downlink data to be transmitted, the base station needs toapply the downlink LBT Cat4 mechanism over an unlicensed carrier forchannel access, so as to transmit the downlink data.

After receiving the uplink grant information, the UE can perform an LBTprocess on a plurality of OFDM symbols before the first uplink subframe,as in the same-carrier scheduling case described above. In a specialcase, when a time-domain length of a gap between an uplink transmissionburst and a downlink transmission burst is smaller than a predeterminedthreshold, which can be 16μs or 25μs, the scheduled UE may apply no LBTmechanism before transmission of the first uplink subframe. For thesubsequent uplink subframes, no LBT mechanism, or a fast LBT mechanismsuch as LBT Cat2, can be applied.

Moreover, in order for the UE to learn the index of the uplink subframeit is on in the burst and/or whether the LBT for the previous subframehas succeeded, the UE can be so notified in accordance with thefollowing schemes.

For a fixed frame structure, the UE can know on which uplink subframe itis scheduled. Thus, the UE can determine which LBT mechanisms orparameter sets to be used for different subframes in a default scheme,which can be the above schemes for same-carrier scheduling orcross-carrier scheduling as described above in this embodiment. Forexample, in the above embodiment, it is determined to use the normal LBTCat4 mechanism for the cross-carrier scheduling and the fast LBTmechanism for the same-carrier scheduling, before transmission of thefirst uplink subframe. Before transmission of the subsequent uplinksubframes, LBT Cat4 mechanisms having successively decreasing CW sizes(the selection of CW sizes is limited to the number of OFDM symbolsavailable for performing LBT processes) can be applied for thecross-carrier scheduling and a fast LBT mechanism can be applied for thesame-carrier scheduling.

For a flexible uplink/downlink subframe structure, there are two schemesfor notifying the UE of the index of the uplink subframe on which it isscheduled in one transmission burst or determining the LBT mechanismand/or LBT mechanism parameter set to be applied.

Scheme 1: The base station can notify the UE explicitly via anindication message whether the scheduled subframe is the first subframeor a subframe that is a particular number of subframes behind the firstsubframe.

Scheme 2: The base station can indicate to the UE via dynamic DCI theLBT mechanism or LBT mechanism parameter set to be applied on thescheduled subframe.

Alternatively, the notification can be carried out via an RRC message.

When the UE scheduled on the first uplink subframe has filed in the LBTprocess in accordance with the LBT mechanism or parameter set, in thenext subframe, the UE can use the same mechanism or parameter set asthat for the first uplink subframe to perform an LBT process.Alternatively, the UE can perform apply the LBT mechanism or LBTmechanism parameter set based on the position of the subframe it is on,or perform channel access using a configured, signaled or default LBTmechanism or LBT mechanism parameter set. In this case, UEs can notifyeach other whether their LBT processes have succeeded, or indicatewhether to use the original LBT mechanism or LBT mechanism parameter setfor channel access or not. Optionally, when the UE has failed for anumber of times in channel access in accordance with the configured LBTmechanism or LBT mechanism parameter set, it can dynamically adjust apriority or the LBT mechanism or parameter set based on an indicationsignaled by a base station, a measurement of feedback information, ameasurement of interference condition, or a priority of a transmittedchannel, a transmitted signal, a transmitted logical channel, or a typeof transmitted traffic (e.g., to raise the priority, so as to performchannel access in accordance with the LBT mechanism or LBT parameter setcorresponding to a higher priority, or perform channel access inaccordance with an LBT mechanism or parameter set having a higherprobability of channel access than the current LBT mechanism orparameter set, so as to provide the UE with a better opportunity inchannel access).

In the above embodiment of the present disclosure, the relatedindication information can include: a size of data packet to betransmitted, a number of successive scheduled subframes, one or morebits configured in DCI signaling, a broadcast scheme, a time-domainlength of a gap between an uplink transmission burst and a downlinktransmission burst, an identity in an LBT list signaled from a basestation, a position of a scheduled subframe in a transmission burst orin successive uplink subframes, a length of one transmission burst,and/or a carrier scenario for transmission of a scheduling instruction.The priority information can include: a QoS priority for a traffic type,or a priority of a channel, a signal and/or a logical channel.Optionally, logical channels having different priority levels can bemapped to corresponding physical transmission channels, such that thephysical transmission channels also have the respective priority levels.The methods for determining the LBT mechanism or LBT mechanism parameterset can be combined, provided that they do not conflict. Also, each ofthese methods can be applied individually for determining the LBTparameter or LBT mechanism.

While the embodiments of the present disclosure have been describedabove, the foregoing is only embodiments (e.g., specific implementationsin the embodiments,) for illustrating, rather than limiting, the presentdisclosure. Various modifications and alternatives in forms and detailscan be made by those skilled in the art without departing from thespirit and scope of the present disclosure. The scope of the presentdisclosure is defined only by the claims as attached.

1. A method for determining Listen Before Talk (LBT) mode, comprising:determining an LBT mechanism and/or an LBT mechanism parameter set basedon related indication information and/or priority information and/ormeasurement information. 2-6. (canceled)
 7. The method of claim 1wherein the LBT mechanism comprises: an LBT mechanism without randomback-off or an LBT mechanism with random back-off. 8-32. (canceled) 33.The method of claim 2, wherein, for a plurality of successive uplinksubframes, said determining the LBT mechanism and/or LBT mechanismparameter set comprises: determining to use the same LBT mechanism orLBT mechanism parameter set or different LBT mechanisms or LBT mechanismparameter sets for the respective uplink subframes. 34-78. (canceled)